Multiplexing acknowledgment messages in response to downlink frames

ABSTRACT

In an example of multi-user wireless communications, an access point may send a downlink frame to multiple stations. Some or all of the stations may generate and transmit their respective uplink frames. The uplink frames from the stations may be aggregated or multiplexed to form a final uplink frame that is received by the access point. The uplink frames may be block acknowledgment or acknowledgment (BA or ACK) frames. Uplink response scheduling may be located in a payload of the downlink frame, in which the uplink response scheduling indicates one or more resource units assigned to the multiple stations for transmitting the uplink frames. In some examples, the uplink response scheduling is in a control field of the payload, in a trigger frame as part of the payload. In some aspects, the downlink frame is part of a multicast transmission. Other methods, apparatus, and computer-readable media are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication No. 62/159,346, entitled “MULTIPLEXING ACKNOWLEDGMENTMESSAGES IN OFDMA,” filed May 10, 2015, U.S. Provisional Application No.62/160,527, entitled “MULTIUSER ACKNOWLEDGMENT MULTIPLEXING,” filed May12, 2015, U.S. Provisional Application No. 62/191,623, entitled“MULTIPLEXING ACKNOWLEDGMENT MESSAGES IN RESPONSE TO DL FRAMES,” filedJul. 13, 2015, and U.S. Provisional Application No. 62/193,305, entitled“MULTIPLEXING ACKNOWLEDGMENT MESSAGES IN RESPONSE TO DL FRAMES,” filedJul. 16, 2015, the entirety of each of which is incorporated herein byreference.

TECHNICAL FIELD

The present description relates in general to wireless communicationsystems and methods, and more particularly to, for example, withoutlimitation, multiplexing acknowledgment messages in response to downlink(DL) frames.

BACKGROUND

Wireless local area network (WLAN) devices are deployed in diverseenvironments. These environments are generally characterized by theexistence of access points and non-access point stations. Increasedinterference from neighboring devices gives rise to performancedegradation. Additionally, WLAN devices are increasingly required tosupport a variety of applications such as video, cloud access, andoffloading. In particular, video traffic is expected to be the dominanttype of traffic in many high efficiency WLAN deployments. With thereal-time requirements of some of these applications, WLAN users demandimproved performance in delivering their applications, includingimproved power consumption for battery-operated devices.

The description provided in the background section may not be assumed tobe prior art merely because it is mentioned in or associated with thebackground section. The background section may include information thatdescribes one or more aspects of the subject technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processor in a wireless communication device.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processor in a wireless communication device.

FIG. 4 illustrates an example of a timing diagram of interframe space(IFS) relationships.

FIG. 5 illustrates an example of a timing diagram of a carrier sensemultiple access/collision avoidance (CSMA/CA) based frame transmissionprocedure for avoiding collision between frames in a channel.

FIG. 6 illustrates a schematic diagram of an example of a format of ahigh efficiency (HE) physical layer convergence procedure (PLCP)protocol data unit (HE PPDU) frame.

FIGS. 7 through 11 illustrate schematic diagrams of examples of adownlink OFDMA frame and an uplink OFDMA frame with varying uplinkmulti-user (MU) acknowledgment assignments.

FIG. 12 illustrates a schematic diagram of an example of a downlinkframe and an uplink frame, where the downlink frame has a trigger framein a payload of the downlink frame.

FIG. 13 illustrates an example of a control field of a data frame.

FIG. 14 illustrates a schematic diagram of an example of a downlinkOFDMA frame and an uplink MU frame from a set of stations.

FIG. 15 illustrates a schematic diagram of an example of a downlink MUframe and an uplink MU frame from a set of stations.

FIGS. 16A through 16C illustrate flow charts of examples of multi-useraggregation methods for data and control frame operation.

In one or more implementations, not all of the depicted components ineach figure may be required, and one or more implementations may includeadditional components not shown in a figure. Variations in thearrangement and type of the components may be made without departingfrom the scope of the subject disclosure. Additional components,different components, or fewer components may be utilized within thescope of the subject disclosure.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious implementations and is not intended to represent the onlyimplementations in which the subject technology may be practiced. Asthose skilled in the art can realize, the described implementations maybe modified in various different ways, all without departing from thescope of the present disclosure. Accordingly, the drawings anddescription are to be regarded as illustrative in nature and notrestrictive.

New multi-user (MU) transmissions, such as downlink (DL) orthogonalfrequency division multiple access (OFDMA) and DL MUmultiple-input/multiple-output (MIMO), provide new opportunities fornext-generation WiFi technology. For example, OFDMA is a technique thatcan be used in WiFi technology in order to enhance the aggregation ofmultiple payloads that are destined to multiple stations (STAs) withinthe same frame. Due to this and other advantages, OFDMA technique isbeing considered for next generation WLAN technologies, including802.11ax which is also referred to as high efficiency (HE) technology.

With OFDMA technique, there comes new opportunities and challenges thatcan be considered in the design of OFDMA signaling and procedures. Amongthe opportunities that are provided by OFDMA is the frequencyselectivity gain, where AP can allocate resources to each STA wherethose allocated resources offer highest frequency-gain for that STA.Using acknowledgement procedures, the access point (AP) can obtain theinformation that is needed to harvest frequency selectivity gain foreach STA in the subsequent DL or uplink (UL) OFDMA frames.

The present disclosure describes methods that can be used among multiplenodes (e.g., between a pair of 802.11 nodes) while they exchange framesin OFDMA or MU MIMO formats. In OFDMA or other MU transmissions, thetransmitter node, commonly an AP in 802.11 use cases, may send an OFDMAframe to several other STAs (or clients). In response, some or all ofthe STAs may send acknowledgment frames in form of an Acknowledgment(ACK) frame or a Block Acknowledgment (BlockAck or BA) frame. One ormore implementations of the present disclosure describe anew uplinkframe with specific formats where multiple STAs (or clients) participatein forming the uplink frame by embedding or multiplexing the STAs' ACKor BA frames into the uplink frame. Hence, several ACK or BA frames maybe embedded into a single MU ACK/BA frame, thereby enhancing the OFDMAoperation or the MU operation using MU MIMO techniques. One or moreimplementations of setting the parameters for the MU ACK/BA frame aredescribed herein.

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network 100. In the wireless communication network 100,such as a wireless local area network (WLAN), a basic service set (BSS)includes a plurality of wireless communication devices (e.g., WLANdevices). In one aspect, a BSS refers to a set of STAs that cancommunicate in synchronization, rather than a concept indicating aparticular area. In the example, the wireless communication network 100includes wireless communication devices 111-115, which may be referredto as stations (STAs).

Each of the wireless communication devices 111-115 may include a mediaaccess control (MAC) layer and a physical (PHY) layer according to anIEEE 802.11 standard. In the example, at least one wirelesscommunication device (e.g., device 111) is an access point (AP). An APmay be referred to as an AP STA, an AP device, or a central station. Theother wireless communication devices (e.g., devices 112-115) may benon-AP STAs. Alternatively, all of the wireless communication devices111-115 may be non-AP STAs in an Ad-hoc networking environment.

An AP STA and a non-AP STA may be collectively called STAs. However, forsimplicity of description, in some aspects, only a non-AP STA may bereferred to as a STA. An AP may be, for example, a centralizedcontroller, a base station (BS), a node-B, a base transceiver system(BTS), a site controller, a network adapter, a network interface card(NIC), a router, or the like. A non-AP STA (e.g., a client deviceoperable by a user) may be, for example, a device with wirelesscommunication capability, a terminal, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal,a mobile subscriber unit, a laptop, a non-mobile computing device (e.g.,a desktop computer with wireless communication capability) or the like.In one or more aspects, a non-AP STA may act as an AP (e.g., a wirelesshotspot).

In one aspect, an AP is a functional entity for providing access to adistribution system, by way of a wireless medium, for an associated STA.For example, an AP may provide access to the internet for one or moreSTAs that are wirelessly and communicatively connected to the AP. InFIG. 1, wireless communications between non-AP STAs are made by way ofan AP. However, when a direct link is established between non-AP STAs,the STAs can communicate directly with each other (without using an AP).

In one or more implementations, OFDMA-based 802.11 technologies areutilized, and for the sake of brevity, a STA refers to a non-AP highefficiency (HE) STA, and an AP refers to an HE AP. In one or moreaspects, a STA may act as an AP.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device. The wireless communication device 200 includes abaseband processor 210, a radio frequency (RF) transceiver 220, anantenna unit 230, a memory 240, an input interface unit 250, an outputinterface unit 260, and a bus 270, or subsets and variations thereof.The wireless communication device 200 can be, or can be a part of, anyof the wireless communication devices 111-115.

In the example, the baseband processor 210 performs baseband signalprocessing, and includes a medium access control (MAC) processor 211 anda PHY processor 215. The memory 240 may store software such as MACsoftware including at least some functions of the MAC layer. The memorymay further store an operating system and applications.

In the illustration, the MAC processor 211 includes a MAC softwareprocessing unit 212 and a MAC hardware processing unit 213. The MACsoftware processing unit 212 executes the MAC software to implement somefunctions of the MAC layer, and the MAC hardware processing unit 213 mayimplement remaining functions of the MAC layer as hardware (MAChardware). However, the MAC processor 211 may vary in functionalitydepending on implementation. The PHY processor 215 includes atransmitting (TX) signal processing unit 280 and a receiving (RX) signalprocessing unit 290. The term TX may refer to transmitting, transmit,transmitted, transmitter or the like. The term RX may refer toreceiving, receive, received, receiver or the like.

The PHY processor 215 interfaces to the MAC processor 211 through, amongothers, transmit vector (TXVECTOR) and receive vector (RXVECTOR)parameters. In one or more aspects, the MAC processor 211 generates andprovides TXVECTOR parameters to the PITY processor 215 to supplyper-packet transmit parameters. In one or more aspects, the PHYprocessor 215 generates and provides RXVECTOR parameters to the MACprocessor 211 to inform the MAC processor 211 of the received packetparameters.

In some aspects, the wireless communication device 200 includes aread-only memory (ROM) (not shown) or registers (not shown) that storeinstructions that are needed by one or more of the MAC processor 211,the PHY processor 215 and/or other components of the wirelesscommunication device 200.

In one or more implementations, the wireless communication device 200includes a permanent storage device (not shown) configured as aread-and-write memory device. The permanent storage device may beanon-volatile memory unit that stores instructions even when thewireless communication device 200 is off. The ROM, registers and thepermanent storage device may be part of the baseband processor 210 or beapart of the memory 240. Each of the ROM, the permanent storage device,and the memory 240 may be an example of a memory or a computer-readablemedium. A memory may be one or more memories.

The memory 240 may be a read-and-write memory, a read-only memory, avolatile memory, a non-volatile memory, or a combination of some or ofthe foregoing. The memory 240 may store instructions that one or more ofthe MAC processor 211, the PHY processor 215, and/or another componentmay need at runtime.

The RF transceiver 220 includes an RF transmitter 221 and an RF receiver222. The input interface unit 250 receives information from a user, andthe output interface unit 260 outputs information to the user. Theantenna unit 230 includes one or more antennas. When multi-inputmulti-output (MIMO) or multi-user MIMO (MU-MIMO) is used, the antennaunit 230 may include more than one antenna.

The bus 270 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal components ofthe wireless communication device 200. In one or more implementations,the bus 270 communicatively connects the baseband processor 210 with thememory 240. From the memory 240, the baseband processor 210 may retrieveinstructions to execute and data to process in order to execute theprocesses of the subject disclosure. The baseband processor 210 can be asingle processor, multiple processors, or a multi-core processor indifferent implementations. The baseband processor 210, the memory 240,the input interface unit 250, and the output interface unit 260 maycommunicate with each other via the bus 270.

The bus 270 also connects to the input interface unit 250 and the outputinterface unit 260. The input interface unit 250 enables a user tocommunicate information and select commands to the wirelesscommunication device 200. Input devices that may be used with the inputinterface unit 250 may include any acoustic, speech, visual, touch,tactile and/or sensory input device, e.g., a keyboard, a pointingdevice, a microphone, or a touchscreen. The output interface unit 260may enable, for example, the display or output of videos, images, audio,and data generated by the wireless communication device 200. Outputdevices that may be used with the output interface unit 260 may includeany visual, auditory, tactile, and/or sensory output device, e.g.,printers and display devices or any other device for outputtinginformation. One or more implementations may include devices thatfunction as both input and output devices, such as a touchscreen.

One or more implementations can be realized in part or in whole using acomputer-readable medium. In one aspect, a computer-readable mediumincludes one or more media. In one or more aspects, a computer-readablemedium is a tangible computer-readable medium, a computer-readablestorage medium, a non-transitory computer-readable medium, amachine-readable medium, a memory, or some combination of the foregoing(e.g., a tangible computer-readable storage medium, or a non-transitorymachine-readable storage medium). In one aspect, a computer is amachine. In one aspect, a computer-implemented method is amachine-implemented method.

A computer-readable medium may include storage integrated into aprocessor and/or storage external to a processor. A computer-readablemedium may be a volatile, non-volatile, solid state, optical, magnetic,and/or other suitable storage device, e.g., RAM, ROM, PROM, EPROM, aflash, registers, a hard disk, a removable memory, or a remote storagedevice.

In one aspect, a computer-readable medium comprises instructions storedtherein. In one aspect, a computer-readable medium is encoded withinstructions. In one aspect, instructions are executable by one or moreprocessors (e.g., 210, 211, 212, 213, 215, 280, 290) to perform one ormore operations or a method. Instructions may include, for example,programs, routines, subroutines, data, data structures, objects,sequences, commands, operations, modules, applications, and/orfunctions. Those skilled in the art can recognize how to implement theinstructions.

A processor (e.g., 210, 211, 212, 213, 215, 280, 290) may be coupled toone or more memories (e.g., one or more external memories such as thememory 240, one or more memories internal to the processor, one or moreregisters internal or external to the processor, or one or more remotememories outside of the device 200), for example, via one or more wiredand/or wireless connections. The coupling may be direct or indirect. Inone aspect, a processor includes one or more processors. A processor,including a processing circuitry capable of executing instructions, mayread, write, or access a computer-readable medium. A processor may be,for example, an application specific integrated circuit (ASIC), adigital signal processor (DSP), or a field programmable gate array(FPGA).

In one aspect, a processor (e.g., 210, 211, 212, 213, 215, 280, 290) isconfigured to cause one or more operations of the subject disclosure tooccur. In one aspect, a processor is configured to cause an apparatus(e.g., a wireless communication device 200) to perform operations or amethod of the subject disclosure. In one or more implementations, aprocessor configuration involves having a processor coupled to one ormore memories. A memory may be internal or external to the processor.Instructions may be in a form of software, hardware or a combinationthereof. Software instructions (including data) may be stored in amemory. Hardware instructions may be part of the hardware circuitrycomponents of a processor. When the instructions are executed orprocessed by one or more processors, (e.g., 210, 211, 212, 213, 215,280, 290), the one or more processors cause one or more operations ofthe subject disclosure to occur or cause an apparatus (e.g., a wirelesscommunication device 200) to perform operations or a method of thesubject disclosure.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processing unit 280 in a wireless communicationdevice. The transmitting signal processing unit 280 of the PHY processor215 includes an encoder 281, an interleaver 282, a mapper 283, aninverse Fourier transformer (IFT) 284, and a guard interval (GI)inserter 285.

The encoder 281 encodes input data. For example, the encoder 281 may bea forward error correction (FEC) encoder. The FEC encoder may include abinary convolutional code (BCC) encoder followed by a puncturing device,or may include a low-density parity-check (LDPC) encoder. Theinterleaver 282 interleaves the bits of each stream output from theencoder 281 to change the order of bits. In one aspect, interleaving maybe applied only when BCC encoding is employed. The mapper 283 maps thesequence of bits output from the interleaver 282 into constellationpoints.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may use multiple instances of the interleaver 282 and multipleinstances of the mapper 283 corresponding to the number of spatialstreams (N_(SS)). In the example, the transmitting signal processingunit 280 may further include a stream parser for dividing outputs of theBCC encoders or the LDPC encoder into blocks that are sent to differentinterleavers 282 or mappers 283. The transmitting signal processing unit280 may further include a space-time block code (STBC) encoder forspreading the constellation points from the number of spatial streamsinto a number of space-time streams (N_(STS)) and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming depending onimplementation. When MU-MIMO is employed, one or more of the blocksbefore reaching the spatial mapper may be provided for each user.

The IFT 284 converts a block of the constellation points output from themapper 283 or the spatial mapper into a time domain block (e.g., asymbol) by using an inverse discrete Fourier transform (IDFT) or aninverse fast Fourier transform (IFFT). If the STBC encoder and thespatial mapper are employed, the IFT 284 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may insert cyclic shift diversities (CSDs) to preventunintentional beamforming. The CSD insertion may occur before or afterthe inverse Fourier transform operation. The CSD may be specified pertransmit chain or may be specified per space-time stream. Alternatively,the CSD may be applied as a part of the spatial mapper.

The GI inserter 285 prepends a GI to the symbol. The transmitting signalprocessing unit 280 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 221 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 230. When MIMO or MU-MIMO is employed, the GI inserter 285 and theRF transmitter 221 may be provided for each transmit chain.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processing unit 290 in a wireless communication device.The receiving signal processing unit 290 of the PHY processor 215includes a GI remover 291, a Fourier transformer (FT) 292, a demapper293, a deinterleaver 294, and a decoder 295.

The RF receiver 222 receives an RF signal via the antenna unit 230 andconverts the RF signal into one or more symbols. In some aspects, the GIremover 291 removes the GI from the symbol. When MIMO or MU-MIMO isemployed, the RF receiver 222 and the GI remover 291 may be provided foreach receive chain.

The FT 292 converts the symbol (e.g., the time domain block) into ablock of the constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT) depending on implementation. Inone or more implementations, the FT 292 is provided for each receivechain.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may further include a spatial demapper for converting the Fouriertransformed receiver chains to constellation points of the space-timestreams, and a STBC decoder (not shown) for despreading theconstellation points from the space-time streams into the spatialstreams.

The demapper 293 demaps the constellation points output from the FT 292or STBC decoder to the bit streams. If the LDPC encoding is used, thedemapper 293 may further perform LDPC tone demapping before theconstellation demapping. The deinterleaver 294 deinterleaves the bits ofeach stream output from the demapper 293. In one or moreimplementations, deinterleaving may be applied only when BCC decoding isused.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may use multiple instances on the demapper 293 and multipleinstances of the deinterleaver 294 corresponding to the number ofspatial streams. In the example, the receiving signal processing unit290 may further include a stream deparser for combining the streamsoutput from the deinterleavers 294.

The decoder 295 decodes the streams output from the deinterleaver 294and/or the stream deparser. For example, the decoder 295 may be an FECdecoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

FIG. 4 illustrates an example of a timing diagram of interframe space(IFS) relationships. In this example, a data frame, a control frame, ora management frame can be exchanged between the wireless communicationdevices 111-115 and/or other WLAN devices.

Referring to the timing diagram 400, during the time interval 402,access is deferred while the medium (e.g., a wireless communicationchannel) is busy until a type of IFS duration has elapsed. At timeinterval 404, immediate access is granted when the medium is idle for aduration that is equal to or greater than a distributed coordinationfunction IFS (DIFS) 410 duration or arbitration IFS (AIFS) 414 duration.In turn, a next frame 406 may be transmitted after a type of IFSduration and a contention window 418 have passed. During the time 408,if a DIFS has elapsed since the medium has been idle, a designated slottime 420 is selected and one or more backoff slots 422 are decrementedas long as the medium is idle.

The data frame is used for transmission of data forwarded to a higherlayer. In one or more implementations, a WLAN device transmits the dataframe after performing backoff if DIFS 410 has elapsed from a time whenthe medium has been idle.

The management frame is used for exchanging management information thatis not forwarded to the higher layer. Subtype frames of the managementframe include a beacon frame, an association request/response frame, aprobe request/response frame, and an authentication request/responseframe.

The control frame is used for controlling access to the medium. Subtypeframes of the control frame include a request to send (RTS) frame, aclear to send (CTS) frame, and an ACK frame. In the case that thecontrol frame is not a response frame of the other frame (e.g., aprevious frame), the WLAN device transmits the control frame afterperforming backoff if the DIFS 410 has elapsed. In the case that thecontrol frame is the response frame of the other frame, the WLAN devicetransmits the control frame without performing backoff if a short IFS(SIFS) 412 has elapsed. The type and subtype of frame may be identifiedby a type field and a subtype field in a frame control field of theframe.

On the other hand, a Quality of Service (QoS) STA may transmit the frameafter performing backoff if AIFS 414 for access category (AC), e.g.,AIFS[AC], has elapsed. In this case, the data frame, the managementframe, or the control frame that is not the response frame may use theAIFS[AC].

In one or more implementations, a point coordination function (PCF)enabled AP STA transmits the frame after performing backoff if a PCF IFS(PIFS) 416 has elapsed. In this example, the PIFS 416 duration is lessthan the DIFS 410 but greater than the SIFS 412. In some aspects, thePIFS 416 is determined by incrementing the SIFS 412 duration by adesignated slot time 420.

FIG. 5 illustrates an example of a timing diagram of a carrier sensemultiple access/collision avoidance (CSMA/CA) based frame transmissionprocedure for avoiding collision between frames in a channel. In FIG. 5,any one of the wireless communication devices 111-115 in FIG. 1 can bedesignated as one of STA1, STA2 or STA3. In this example, the wirelesscommunication device 111 is designated as STA1, the wirelesscommunication device 112 is designated as STA2, and the wirelesscommunication device 113 is designated as STA3. While the timing of thewireless communication devices 114 and 115 is not shown in FIG. 5, thetiming of the devices 114 and 115 may be the same as that of STA2.

In this example, STA1 is a transmit WLAN device for transmitting data,STA2 is a receive WLAN device for receiving the data, and STA3 is a WLANdevice that may be located at an area where a frame transmitted from theSTA1 and/or a frame transmitted from the STA2 can be received by theSTA3.

The STA1 may determine whether the channel (or medium) is busy bycarrier sensing. The STA1 may determine the channel occupation based onan energy level on the channel or correlation of signals in the channel.In one or more implementations, the STA1 determines the channeloccupation by using a network allocation vector (NAV) timer.

When determining that the channel is not used by other devices duringthe DIFS 410 (e.g., the channel is idle), the STA1 may transmit an RTSframe 502 to the STA2 after performing backoff. Upon receiving the RTSframe 502, the STA2 may transmit a CTS frame 506 as a response of theCTS frame 506 after the SIFS 412.

When the STA3 receives the RTS frame 502, the STA3 may set a NAV timerfor a transmission duration representing the propagation delay ofsubsequently transmitted frames by using duration information involvedwith the transmission of the RTS frame 502 NAV(RTS) 510). For example,the STA3 may set the transmission duration expressed as the summation ofa first instance of the SIFS 412, the CTS frame 506 duration, a secondinstance of the SIFS 412, a data frame 504 duration, a third instance ofthe SIFS 412 and an ACK frame 508 duration.

Upon receiving a new frame (not shown) before the NAV timer expires, theSTA3 may update the NAV timer by using duration information included inthe new frame. The STA3 does not attempt to access the channel until theNAV timer expires.

When the STA1 receives the CTS frame 506 from the STA2, the STA1 maytransmit the data frame 504 to the STA2 after the SIFS 412 elapses froma time when the CTS frame 506 has been completely received. Uponsuccessfully receiving the data frame 504, the STA2 may transmit the ACKframe 508 after the SIFS 412 elapses as an acknowledgment of receivingthe data frame 504.

When the NAV timer expires, the STA3 may determine whether the channelis busy by the carrier sensing. Upon determining that the channel is notused by the other WLAN devices (e.g., STA1, STA2) during the DIFS 410after the NAV timer has expired, the STA3 may attempt the channel accessafter a contention window 418 has elapsed. In this example, thecontention window 418 may be based on a random backoff.

Note that an ACK frame is sent to acknowledge the successful receptionof a frame by a recipient (e.g., STA2). In one or more implementations,a recipient (e.g., STA2) sends a frame referred to as a blockacknowledgment (Block Ack, BlockAck or BA) to acknowledge the successfulreception of multiple consecutive frames at once. In this example, aBlock Ack mechanism improves channel efficiency by aggregating severalacknowledgments into one frame. There are two types of Block Ackmechanisms: immediate and delayed. Immediate Block Ack is suitable forhigh-bandwidth, low-latency traffic while the delayed Block Ack issuitable for applications that tolerate moderate latency. In FIG. 5, theSTA with data to send using the Block Ack mechanism is referred to asthe originator, and the receiver of that data as the recipient.

The Block Ack mechanism is initialized by an exchange of add blockacknowledgment (ADDBA) Request/Response frames. After initialization,blocks of quality-of-service (QoS) data frames may be transmitted fromthe originator (e.g., a STA such as an AP) to the recipient (e.g., aSTA). A block may be initiated within a polled transmission opportunity(TXOP) or by winning an enhanced distributed channel access (EDCA)contention. The number of frames in the block may be limited, and theamount of state that is to be kept by the recipient may be bounded. TheMPDUs within the block of frames are acknowledged by a BlockAck frame,which is requested by a BlockAckReq frame. The Block Ack mechanism doesnot require the setting up of a traffic stream (TS); however, QoS STAsusing the TS facility may select to signal their intention to use theBlock Ack mechanism for the scheduler's consideration in assigningTXOPs. Acknowledgments of frames belonging to the same trafficidentifier (TID), but transmitted during multiple TXOPs, may also becombined into a single BlockAck frame. The Block Ack mechanism allowsthe originator to have flexibility regarding the transmission of dataMPDUs. The originator may split the block of frames across TXOPs,separate the data transfer and the Block Ack exchange, and interleaveblocks of MPDUs carrying all or part of MAC service data units (MSDUs)or aggregate MSDUs (A-MSDUs) for different TIDs or receiving stationaddresses (RAs).

FIG. 6 illustrates a schematic diagram of an example of a format of ahigh efficiency (HE) physical layer convergence procedure (PLCP)protocol data unit (HE PPDU) frame 600. A transmitting STA generates thePPDU frame 600 and transmits the PPDU frame 600 to a receiving STA. Thereceiving STA receives, detects, and processes the PPDU frame 600. ThePPDU frame 600 includes an L-STF field 601, an L-LTF field 602, an L-SIGfield 603, an RL-SIG field 604, an HE-SIG-A field 605, an HE-SIG-B field606, an HE-STF field 607, an HE-LTF field 608, and an HE-DATA field 609.The HE-SIG-A field 605 includes N_(HESIGA) symbols 610, the HE-SIG-Bfield 606 includes N_(HESIGB) symbols 611, the HE-LTF field 608 includesN_(HELTF) symbols 612, and the HE-DATA field 609 includes N_(DATA)symbols 613.

An HE frame may be referred to as an OFDMA frame, a PPDU, a PPDU format,an OFDMA PPDU, an MU PPDU, another similar term, or vice versa. An HEframe may be simply referred to as a frame for convenience. In one ormore implementations, an AP may transmit a frame for downlink (DL) usinga frame format shown in this figure or a variation thereof (e.g.,without any or some portions of an HE header). A STA may transmit aframe for uplink (UL) using a frame format shown in this figure or avariation thereof (e.g., without any or some portions of an HE header).

Referring to FIG. 6, the HE frame 600 contains a header and a datafield. The header includes a legacy header comprised of a legacy shorttraining field (L-STF), a legacy long training field (L-LTF), and alegacy signal (L-SIG) field. These legacy fields contain symbols basedon an early design of an IEEE 802.11 specification. The L-STF, L-LTF,and L-SIG fields may be 8 μs, 8 μs, and 4 μs, respectively. Presence ofthese symbols can make any new design compatible with the legacy designsand products. The legacy header may be referred to as a legacy preamble.In one or more aspects, the term header may be referred to as apreamble.

In one or more implementations, the legacy STF, LTF, and SIG symbols aremodulated/carried with FFT size of 64 on a 20 MHz sub-channel and areduplicated every 20 MHz if the frame has a channel bandwidth wider than20 MHz (e.g., 40 MHz, 80 MHz, 160 MHz). Therefore, the legacy field(i.e., the STF, LTF, and SIG fields) occupies the entire channelbandwidth of the frame. The L-STF field may be utilized for packetdetection, automatic gain control (AGC), and coarse frequency-offset(FO) correction. In one aspect, the L-STF field does not utilizefrequency domain processing (e.g., FFT processing) but rather utilizestime domain processing. Thus, in one aspect, the L-STF field is notaffected by the channel dispersion. The L-LTF field may be utilized forchannel estimation, fine frequency-offset correction, and symbol timing.The L-SIG field includes one orthogonal frequency division multiplexing(OFDM) symbol. Thus, in one aspect, the term L-SIG field may be usedinterchangeably with L-SIG symbol. In one or more aspects, the L-SIGfield may contain information indicative of a data rate and a length(e.g., in bytes) associated with the HE frame 600, which may be utilizedby a receiver of the HE frame 600 to calculate a time duration of atransmission of the HE frame 600.

The header may also include an HE header comprised of an HE-SIG-A fieldand an HE-SIG-B field. The HE-SIG-A field may sometimes be referred tosimply as a SIG-A field. These fields contain symbols that carry controlinformation that may be vital regarding each PLCP service data unit(PSDU) and regarding the radio frequency (RF), PHI, and MAC propertiesof a PPDU. Several sub-fields may be located either in the HE-SIG-Aand/or HE-SIG-B fields. In one aspect, the HE-SIG-A field can becarried/modulated using an FFT size of 64 on a 20 MHz basis. TheHE-SIG-B field can be carried/modulated using an FFT size of e.g., 64 or256 on a 20 MHz basis depending on implementation. The HE-SIG-A andHE-SIG-B fields may occupy the entire channel bandwidth of the frame. Insome aspects, the size of the HE-SIG-A field and/or the HE-SIG-B fieldis variable. In other words, the number of symbols contained in theHE-SIG-A field and/or HE-SIG-B field can vary from frame to frame. AnHE-SIG-B field is not always present in all frames. In some cases,single user (SU) packets and UL trigger-based packets do not contain theHE-SIG-B field. To facilitate decoding of the HE frame 600 by areceiver, the size of (e.g., number of symbols contained in) theHE-SIG-B field may be indicated in the HE-SIG-A field. In some aspects,the HE header also includes a repeated L-SIG (RL-SIG) field, whosecontent is the same as the L-SIG field.

For a 20 MHz channel, an FFT size of 64 is associated with a discreteFourier transform (DFT) period of 3.2 μs and a subcarrier spacing of312.5 kHz. For a 20 MHz channel, an FFT size of 256 is associated with aDFT period of 12.8 μs and a subcarrier spacing of 78.125 kHz. The DFTperiod may also be referred to as an inverse DFT period (IDFT) or anIDFT/DFT period. The DFT period may be denoted as T_(DFT). Thesubcarrier spacing may be referred to as a subcarrier frequency spacingand may be denoted as Δ_(F). The subcarrier spacing may be obtained bydividing the channel bandwidth by the FFT size. The subcarrier spacingis the reciprocal of the DFT period.

The HE header may further include HE-STF and HE-LIT fields, whichcontain symbols used to perform necessary RF and PHY processing for eachPSDU and/or for the whole PPDU. The HE-LTF symbols may bemodulated/carried with an FFT size of 256 for 20 MHz bandwidth andmodulated over the entire bandwidth of the frame. Thus, the HE-LIT fieldmay occupy the entire channel bandwidth of the frame. In one aspect, anHE-LTF sequence may be utilized by a receiver to estimate MIMO channelbetween the transmitter and the receiver. Channel estimation may beutilized to decode data transmitted and compensate for channelproperties (e.g., effects, distortions). For example, when a preamble istransmitted through a wireless channel, various distortions may occur,and a training sequence in the HE-LTF field is useful to reverse thedistortion. This may be referred to as equalization. To accomplish this,the amount of channel distortion is measured. This may be referred to aschannel estimation. In one aspect, channel estimation is performed usingan HE-LTF sequence, and the channel estimation may be applied to otherfields that follow the HE-LTF sequence.

The HE-STF symbols may have a fixed pattern and a fixed duration. Forexample, the HE-STF symbols may have a predetermined repeating pattern.In one aspect, the HE-STF symbols do not require FFT processing. The HEframe 600 may include the data field, represented as HE-DATA, thatcontains data symbols. The data field may also be referred to as apayload field, data, payload, PSDU, or Media Access Control (MAC)Protocol Data Units (MPDU) (e.g., MAC frame).

In one or more aspects, additional one or more HE-LTF fields may beincluded in the header. For example, an additional HE-LTF field may belocated after a first HE-LTF field. The HE-LTF fields may be, forexample, modulated/carried with FFT size of 64 on a 20 MHz channel andmay be included as part of the first part of the HE frame 600. In one ormore implementations, a TX signal processing unit 280 (or an IFT 284)illustrated in FIG. 3A may carry out the modulation described in thisparagraph as well as the modulations described in other paragraphsabove. In one or more implementations, an RX signal processing unit 290(or an FT 292) may perform demodulation for a receiver.

FIGS. 7 through 12 show examples of downlink DL frames and uplink (UL)frames. In one aspect of the disclosure below, a downlink frame mayrefer to a DL OFDMA frame, a HE DL OFDMA frame, a DL OFDMA PPDU, a HE DLOFDMA PPDU, a DL PPDU, a DL MU frame, a DL MU MIMO frame, or vice versa.In one aspect, an uplink frame may refer to a UL OFDMA frame, a HE ULOFDMA frame, a UL OFDMA PPDU, a HE UL OFDMA PPDU, a UL PPDU, a UL MUframe, a UL MU MIMO frame, a MU ACK frame, a MU ACK PPDU, or vice versa.In one aspect, a PPDU refers to a HE PPDU or an OFDMA PPDU. In oneaspect, a PPDU is a downlink frame (e.g., 700) or an uplink frame (e.g.,720). A frame may refer to a PPDU, a Media Access Control (MAC) ProtocolData Unit (MPDU) MPDU, or an A-MPDU.

In one or more aspects, a DL OFDMA frame (e.g., 700) is sent to a set ofSTAs. After a predetermined time period (e.g., SIB) after the receipt ofthe DL OFDMA frame, each STA of the same set of the STAs or each STA ofa subset of the STAs replies with an individual ACK frame or BA frame inthe form of a MU ACK frame (or a UL OFDMA PPDU 720). In one aspect, aPHY processor 215 or a TX signal processing unit 280 generates theframes and their components shown in FIGS. 7 through 12.

In FIGS. 7 through 12, the horizontal dimension represents the timedimension or number of OFDM symbols, whereas the vertical dimensionrepresents the frequency dimension, number of tones or number ofsub-carriers. Note that for a given FFT size, the number of tones isgiven, however, depending on the sub-carrier spacing, two OFDM symbolswith e.g., FFT=64 and FFT=256 can occupy the same bandwidth. In one ormore implementations of the present disclosure, a sub-band refers to aset of contiguous tones or subcarriers that as a whole are assigned fora payload whose expected destination is a single STA, or a set of STAs.In one or more implementations, a sub-band is a horizontal partition ofan OFDMA PPDU or frame where a set of contiguous tones for a contiguousset of OFDM symbols are designated for a given payload whose expecteddestination is a STA or a set of STAs.

Legacy STF/LTF/SIG (e.g., 701) are several symbols based on an earlydesign of an IEEE 802.11 specification. Presence of these symbols canmake any new design compatible with the legacy designs and products. Inone or more implementations, the legacy STF, LTF and SIG symbols aremodulated/carried with FFT size of 64 on a 20 MHz sub-channel and areduplicated every 20 MHz if the DL OFDMA PPDU has a bandwidth wider than20 MHz.

In one or more aspects, the HE SIG-A and HE SIG-B are symbols that carrycontrol information that may be vital regarding each PSDU and regardingthe radio frequency (RF), PHY and MAC properties of the PPM. In thepresent disclosure, several fields are located either in HE SIG-A and/orHE SIG-B. The HE SIG-A and HE SIG-B can be carried/modulated using FFTsize of 64 or 256 depending on implementation. In some aspects, the HESIG-B is not present in all UL OFDMA PPDUs.

The HE STF and HE LTF are symbols used to perform necessary RF and PHYprocessing for each PSDU and/or for the whole PPDU. Depending on whetherthe HE STF/LTF symbols are beamformed, there may be two sets of suchsymbols.

FIGS. 7 through 12 illustrate schematic diagrams of examples of downlinkand uplink frames in an OFDMA exchange among WLAN devices. Withreference to these figures, in one or more implementations, OFDMA-based802.11 technology is utilized, and for the sake of brevity, a STA refersto a non-AP HE STA, and an AP refers to a HE AP. In one or more aspects,a STA may act as an AP.

In FIGS. 7 through 12, a reference numeral 700 is used for a DL OFDMAPPDU, a reference numeral 709 is used for a payload section of a DLOFDMA PPDU, a reference numeral 720 is used for a UL OFDMA PPDU, and areference numeral 726 is used for a payload section of a UL OFDMA PPDU,all for simplicity and convenience. These components with the samereference numerals have certain characteristics that are the same, butas different figures illustrate different examples, the same referencenumeral does not indicate that a component with the same referencenumeral has the exact same characteristics. While the same referencenumerals are used for these components, examples of differences withrespect to a component are described in connection with differentfigures.

In one aspect, a DL OFDMA PPDU 700 is followed by a UL OFDMA PPDU 720after a predetermined time period (e.g., SIFS) has elapsed. In oneaspect, a DL OFDMA PPDU 700) includes a header (e.g., 710) and a payload(e.g., 709). In one aspect, a UL OFDMA PPDU (e.g., 720) includes aheader (e.g., 721) and a payload (e.g., 726).

In one aspect, a header is referred to as a preamble header, a preamble,a header section, or vice versa. For the sake of brevity, a header mayrefer to a component of a header. Thus, in one aspect, a header mayrefer to one or more headers (e.g., a header 710 for headers 701, 702,703 and 704; a header 701 for legacy STF, LTF and SIG). In one aspect, aheader is associated with a bandwidth of a PPDU. In one example, for agiven bandwidth (e.g., 80 MHz) of a PPDU, a header is modulated on theentire bandwidth of the PPDU (e.g., entire 80 MHz). In another example,a header is modulated on a sub-channel (e.g., 20 MHz sub-channel) of thebandwidth 80 MHz) and the modulated signal is duplicated on each of theremaining sub-channels (e.g., remaining three 20 MHz sub-channels) ofthe bandwidth.

In one aspect, a payload includes multiple payloads or PSDUs. The termPSDU refers to a PLCP service data unit. A PSDU for downlink (e.g., 705)is associated with a sub-band of the bandwidth of its PPDU (e.g., 700)and is modulated using the sub-band rather than the entire bandwidth ofthe PPDU. A PSDU for uplink (e.g., 722) is associated with a sub-band ofthe bandwidth of its PPDU (e.g., 720) and is modulated using thesub-band rather than the entire bandwidth of the PPDU. In one aspect,the modulation involves inverse Fourier transformation performed, forexample, by an inverse Fourier transformer 284 in FIG. 3A.

A MU ACK frame in the form of an UL OFDMA PPDU 720 includes ACK or BAframes from the STAs e.g., STAs that receive and determine that anassociated payload in the DL OFDMA PPDU 700 has an ACK policy field in aQoS control field set to 00 or “Normal Ack or Implicit Block AckRequest”). For example, STA1 determines (e.g., detects, searches for,checks, acknowledges and/or verifies) the ACK policy field in the QoScontrol field included in a PSDU payload 705 of the DL OFDMA PPDU 700received by STA1.

Referring to FIG. 7, in an example of operation, an AP (e.g., wirelesscommunication device 111) transmits the DL OFDMA PPDU 700 in a HE PPDUformat. In one aspect, the HE PPDU format is comprised of a legacyheader, a HE header (e.g., a HE SIG-A 702, a HE STF/LTF 703, a HE SIG-B704) and a payload section 709 (e.g., PSDUs). In some aspects, thelegacy header 701 consists of L-STF, L-LTF and L-SIG. In one aspect,L-STF, L-LTF and L-SIG symbols are modulated with an FFT size of 64 on a20 MHz sub-channel and the modulated symbols are duplicated on every 20MHz sub-channel if the DL OFDMA PPDU 700 has a bandwidth wider than 20MHz.

In one or more implementations, a HE PLCP is composed of all or part ofthe HE SIG-A 702, the HE STF/LTF 703 (which are HE STF and HE LTF) andthe HE SIG-B 704. The HE SIG-A 702 is modulated with an FFT size of 64and duplicated on all of the 20 MHz sub-channels that the DL OFDMA PPDU700 consists of, if the DL OFDMA PPDU 700 has a bandwidth wider than 20MHz. The HE STF/LTF 703 and the HE SIG-B 704 are modulated with an FFTsize of 256 and modulated over the entire bandwidth of the DL OFDMA PPDU700.

The payload section 709 includes payloads (e.g., PSDUs) assigned tomultiple STAs, and is modulated using an FFT size of 256. In thisregard, the payloads are associated with STA1, STA2, STA3, and STA4, Forexample, the PSDU payload 705 is associated with STA1, PSDU payload 706is associated with STA2, PSDU payload 707 is associated with STA3, andPSDU payload 708 is associated with STA4. The AP transmits the payloadsthrough sub-bands of possibly varying bandwidth, and possiblynon-contiguous sub-bands for STAs in one aspect, each set of sub-bandsis associated with its respective PSDU. In one aspect, each set ofsub-bands is associated with its respective STA. In one aspect, thenumber of assigned sets of sub-bands is the same as the number of STAs.In FIG. 7, the sub-bands assigned to STA1, STA2, STA3, and STA4 haveequal bandwidth and the sub-bands are contiguous; however, the proceduredescribed in the present disclosure does not require contiguous or equalbandwidth for sets of assigned sub-bands.

A DL OFDMA PPDU has a predetermined bandwidth, e.g., 20 MHz, 40 MHz, 80MHz, 160 MHz, or 80+80 MHz (i.e., two 80 MHz). A sub-band is a portionof the bandwidth of a DL OFDMA PPDU. For example, when the bandwidth ofa DL OFDMA PPDU is 20 MHz, and there are four STAs, each of thesub-bands associated with a respective one of the STAs is 5 MHz inbandwidth. When the bandwidth is 40 MHz, each of the four sub-bandsassociated with a respective one of the four STAs may be 10 MHz inbandwidth. When the bandwidth is 80 MHz, each of the four sub-bandsassociated with a respective one of the four STAs may be 20 MHz inbandwidth. These are merely examples, and the present disclosure is notlimited to these examples. A bandwidth (e.g., 20 MHz, 40 MHz, 80 MHz,160 MHz, or 80+80 MHz) of a DL OFDMA PPDU may be referred to as a DLbandwidth, a DL PPDU bandwidth, or an overall DL bandwidth. A bandwidth(e.g., 20 MHz, 40 MHz, 80 MHz, 160 MHz, or 80+80 MHz) of a UL OFDMA PPDUmay be referred to as a UL bandwidth, a UL PPDU bandwidth, or an overallUL bandwidth. An overall bandwidth or an entire bandwidth may refer to aDL bandwidth or a UL bandwidth.

Upon the completion of the sequence of (a) the receipt of the DL OFDMAPPM 700 by the STAs and (b) the passing of the time period of the SIFS,each of the STAs that determines that its ACK policy field in the QoScontrol field of its PSDU (e.g., data frame) in the DL OFDMA PPDU 700 isset to 00 or “Normal Ack or Implicit Block Ack Request,” transmits itsACK or BA frame simultaneously in the format of the UL OFDMA PPDU 720(which may be referred to as a MU ACK frame). The UL OFDMA PPDU 720 iscomposed of a legacy PLCP 721 and a payload section 726, which aretransmitted by all of the STAs that participate in forming the MU ACKframe.

In this example, each STA transmits its uplink frame that includes aheader (e.g., a legacy PLCP 721) and its acknowledgment frame (e.g., oneof 722, 723, 724 or 725 associated with the STA). The UL OFDMA PPDU 720is an uplink frame that includes a header (e.g., a legacy PLCP 721) andthe acknowledgment frames (e.g., all of 722, 723, 724 or 725) from allof the STAs that participate in forming the MU ACK frame.

For example, STA1 generates and transmits a first uplink frame comprisedof a legacy PLCP 721 and an acknowledgment frame 722 (e.g., an ACK or BAframe), STA2 generates and transmits a second uplink frame comprised ofa legacy PLCP 721 and an acknowledgment frame 723 (e.g., an ACK or BAframe), STA3 generates and transmits a third uplink frame comprised of alegacy PLCP 721 and an acknowledgment frame 724 (e.g., an ACK or BAframe), and STA4 generates and transmits a fourth uplink frame comprisedof a legacy PLCP 721 and an acknowledgment frame 725 (e.g., an ACK or BAframe). All of the first, second, third and fourth uplink frames are RFcombined or aggregated to form a final uplink frame, which is the ULOFDMA PPDU 720, for the AP. As all of the STAs are synchronized andtransmit their respective uplink frames (e.g., the first, second, thirdand fourth uplink frames) at the same time (e.g., upon the completion ofa predetermined time period of SIFS), all of these frames aremultiplexed simultaneously into the uplink frame 720.

In one or more aspects, for an uplink frame, each STA (e.g., each ofSTA1, STA2, STA3 and STA4) generates a legacy PLCP 721 utilizing theentire UL channel bandwidth. A legacy PLCP 721 of a STA is associatedwith the entire UL channel bandwidth (rather than a sub-band). A legacyPLCP 721 of a STA occupies the entire UL channel bandwidth. In oneaspect, a STA modulates a legacy PLCP 721 utilizing the entire ULchannel bandwidth. For example, if the UL channel bandwidth is 80 MHz, aSTA modulates the legacy PLCP with FFT size of 64 on a 20 MHzsub-channel and duplicates the modulated legacy PLCP on the remainingthree 20 MHz sub-channels so that the legacy PLCP occupies the entire 80MHz bandwidth.

In one or more aspects, each STA generates an acknowledgment frame(e.g., 722, 723, 724, or 725) utilizing a sub-band assigned to the STA(rather than the entire UL channel bandwidth). An acknowledgment frameof a STA is associated with a sub-band (rather than the entire channelbandwidth). An acknowledgment frame of a STA occupies a sub-bandassigned to the STA. A sub-band is a portion of a UL channel bandwidth,and a STA modulates an acknowledgment frame utilizing a sub-band.

In one aspect, a baseband processor (e.g., a baseband processor 210 inFIG. 2, or more specifically, e.g., a MAC processor 211) of a STA cangenerate and provide an acknowledgment frame. In one aspect, a basebandprocessor (e.g., a baseband processor 210 in FIG. 2, or morespecifically, e.g., a PHY processor 215 or a TX signal processing unit280) of a STA can generate and facilitate transmission of an uplinkframe directed to an AP.

In one aspect, the UL OFDMA PPDU 720 has a bandwidth that is the same asthe bandwidth of the preceding DL OFDMA PPDU 700. The legacy PLCP 721(of each of the first, second, third and fourth uplink frames) isassociated with the bandwidth of the UL OFDMA PPDU 720. Likewise, thelegacy PLCP 721 of the UL OFDMA PPDU 720 is associated with thebandwidth of the UL OFDMA PPDU 720.

Each of the acknowledgment frames of the STAs is associated itsrespective sub-band, where a sub-band is a portion of the bandwidth ofthe UL OFDMA PPDU 720.

In some aspects, the legacy PLCP 721 (of each of the first, second,third and fourth uplink frames and the UL OFDMA PPDU 720) consists ofthe STF, the LTF and the SIG symbols, which are modulated with an FFTsize of 64 on a 20 MHz sub-channel, and the modulated signal isduplicated every 20 MHz sub-channel if the UL OFDMA PPDU 720 has abandwidth wider than 20 MHz. A legacy PLCP 721 thus utilizes the entirebandwidth (e.g., by duplication as described above).

In one aspect, the payload section 726 has multiple payloads (e.g.,PSDUs) for of the STAs that participate in forming the MU ACK frame, andis modulated using an FFT size of 256. In this regard, a payload isassociated with its respective one of STA1, STA2, STA3, and STA4. InFIG. 7, the STA1, the STA2, the STA3 and the STA4 participate inthrilling the UL OFDMA PPDU 720. For example, the ACK/BA payload 722 isassociated with STA1, ACK/BA payload 723 is associated with STA2, ACK/BApayload 724 is associated with STA3, and ACK/BA payload 725 isassociated with STA4.

FIG. 8 shows a similar exchange as in FIG. 7 except that a UL OFDMA PPDU800 has additional signaling between the legacy PLCP 721 and the payloadsection 726. In this regard, examples of differences are described inFIG. 8 for purposes of simplicity.

In this configuration, the UL OFDMA PPDU 800 is comprised of not onlythe legacy PLCP 721 and the payload section 726 but also a partial HEPLCP. In one or more implementations, the partial HE PLCP consists of aHE SIG-A field 801, which is modulated using an FFT size of 64 andduplicated on all of the 20 MHz sub-channels that the UL OFDMA PPDU 720consists of. The HE SIG-A field 801 may be present either with multiplesymbols or only with a first symbol referred to as a HE SIG-A1.

In one aspect, the content of a HE SIG-A field 801 of a UL OFDMA PPDU800 from an intended STA is already known by the recipient (e.g., AP).In one aspect, the HE SIG-A is useful for unintended STAs to obtain somevital information about the frame and defer properly, and suchinformation can be provided in HE SIG-A or the first symbol of the HESIG-A. Examples of the above-mentioned vital information are: (a) theduration of the uplink (MU UL) frame and in this the duration of MU ACKframe and (b) an indication whether there can be a (downlink) responseframe to the uplink (MU UL) frame. Unintended STA(s) may be one or moreSTAs that are not intended (or required by the AP) to participate informing a MU ACK frame; however, they may monitor the wireless medium inorder to send their frame. Given the possibility of such unintendedSTAs, and given that HE SIG-A is encoded robustly so that it can beoften decoded successfully; the above-mentioned vital information givessome information about the status of the medium to the unintended STAs.

In this example, the bandwidth of the DL OFDMA PPDU 700 and thebandwidth of the subsequent UL OFDMA PPDU 800 are the same. For example,the bandwidth may be 20 MHz where each of the sub-bands assigned to eachSTA has 5 MHz of bandwidth, or the bandwidth may be 80 MHz where each ofthe sub-bands has 20 MHz of bandwidth.

FIG. 9 illustrates a schematic diagram of an example of a downlink frameand an uplink frame for an OFDMA exchange among WLAN devices. In thiscase, the DL OFDMA PPDU 900 includes a header section 710 comprised ofthe legacy PLCP 701, the HE SIG-A 702, the HE STF/LTF 703 and the HESIG-B 704. The payload section 709 contains multiple PSDU payloads wherePSDU 901 is associated with STA1, PSDU 902 is associated with STA2, PSDU903 is associated with STA3, PSDU 904 is associated with STA4 and PSDU905 is associated with STA5. The UL OFDMA. PPDU 920 includes the legacyPLCP 721 and the payload section 726. The payload section 726 includesmultiple ACK/BA payloads where ACK/BA payload 921 is associated withSTA1, ACK/BA payload 922 is associated with STA2, ACK/BA payload 923 isassociated with STA3, ACK/BA payload 924 is associated with STA4, andACK/BA payload 925 is associated with STA5.

In this case, a similar exchange as in FIG. 7 is illustrated except thatthe STAs that receive payloads in the DL OFDMA PPDU 900 do not all havethe same sub-band bandwidths. For example, the overall (or entire)bandwidth of DL OFDMA PPDU 900 (or UL OFDMA PPDU 920) may be 40 MHz,where each of the three STAs (e.g., each of STA3, STA4 and STA5) has asub-band with 10 MHz bandwidth, and each of the two STAs (e.g., each ofSTA1 and STA2) has a sub-band with 5 MHz bandwidth. In this example,each STA responds with an ACK or a BA frame in the same sub-band thatthe STA has received its payload in the DL OFDMA PPDU 900 after the SIFS412 has elapsed. Note that due to different sizes of the sub-bands, oneor more of the STAs may need to pad the respective one or more payloadsfor the ACK or BA frame so that all of the PSDUs formed by theparticipating STAs in the payload section 726 have an equal timeduration. By having the STAs respond with the same sub-band bandwidth asthe downlink sub-band bandwidth, the amount of processing and/oroverhead may be minimized during the generation of the UL OFDMA PPDU 920thereby increasing efficiency in the overall acknowledgment mechanism.

FIG. 10 illustrates a schematic diagram of an example of a downlinkframe and an uplink frame for an OFDMA exchange among STAs. In thiscase, the exchange is similar to FIG. 7 and FIG. 9, except that the STAsthat receive payloads in the DL OFDMA PPDU 700 do not all have the samesub-band bandwidths and one of the STAs does not respond with an ACK orBA, for example, because the corresponding ACK policy field in the QoScontrol field of the DL OFDMA PPDU 700 is not set to “Normal Ack orImplicit Block Ack Request,” because the DL PSDU has been received bythe STA in error, or because there has been an error or failure inreceipt. For example, STA3 does not transmit an uplink frame with an ACKor BA for a UL OFDMA PPDU 1000 because, among others, the STA3determines that it is instructed not to participate in forming a MU ACKframe (e.g., STA3 did not find the ACK policy field identifying the STA3as a participant in the MU ACK frame formation), or the associated PSDU(e.g., PSDU payload 904) has been received in error by the STA3. A PSDUpayload may not be received by the corresponding STA due to one or morereasons, including but not limited to, the PSDU was corrupted duringtransmission, the transmission was impacted by interference, the QoScontrol field indicated that the ACK policy field was not set for MU ACKparticipation, etc.

In one or more implementations, the AP does not detect that there is amissing PSDU in one or more received sub-bands assigned to thecorresponding STAs, e.g., STA3, and may process the received signal(e.g., the UL OFDMA PPDU 1000). However, after processing the PSDU inthe sub-band location and obtaining the frame check sequence (FCS), theAP (e.g., 210 or 211 of the AP) can identify that neither ACK nor BA ispresent in the sub-band location. In this regard, and if the APoriginally had not set the QoS control field of the DL OFDMA PPDU to“Normal Ack or Implicit Block Ack Request,” the AP can determine thatthe corresponding PSDU (e.g., 904) can need to be retransmitted for theassociated STA (e.g., STA3), and the AP may retransmit the DL OFDMA PPDUthat contains the PSDU 904.

In the process of forming the DL OFDMA PPDU 900 and the UL OFDMA PPDU1000, a TXVECTOR parameter and a RXVECTOR parameter are employed (asdescribed with reference to FIG. 2), each of which is denoted by asubcarriers list, a sub-band list, or an RU list (e.g.,SUBCARRIERS_LIST, SUBBAND_LIST, or RU_LIST). The SUBCARRIERS_LIST is ascalar value that may be used in a HE OFDMA PPDU or a HE OFDMA PPDU witha partial PLCP or PRY header. In some aspects, the SUBCARRIERS_LIST inthe TXVECTOR/RXVECTOR parameters is a set of scalar values where eachscalar value indicates a set of sub-carriers, or equivalently a sub-bandor set of sub-bands (where each sub-band is a set of sub-carriers). Inone or more implementations, a SUBCARRIERS_LIST is a predetermined list(a priori) known to the AP and all STAs. In this case, theSUBCARRIERS_LIST represents a listing of index values, where each indexvalue represents a corresponding sub-band allocation for a subsequentacknowledgment frame. As such, the AP can only need to indicate an indexof the SUBCARRIERS_LIST in order to assign a particular sub-band to aSTA.

In one or more implementations, a SUBCARRIERS_LIST is included in aTXVECTOR parameter, and a MAC processor 211 (FIG. 2) sends the TXVECTORparameter with the SUBCARRIERS_LIST to a PHY processor 215 no that thePHY processor 215 can determine which set of sub-carriers (or set ofsub-bands) is used to place the payload in a DL OFDMA PPDU 900. In oneor more implementations, a SUBCARRIERS_LIST may optionally be includedin an RXVECTOR parameter, and a PHY processor 215 sends the RXVECTORparameter with the SUBCARRIERS_LIST to a MAC processor 211 so that theMAC processor 211 can determine from which set of sub-carriers (or setof sub-bands) of the OFDMA PPDU 1000, the received payload 726 wasobtained.

In forming the UL OFDMA PPDU 1000 (or a MU ACK frame), eachparticipating STA forms a frame in the form of a MU ACK frame, asfollows: (a) the legacy PLCP, (b) the partial HE PLCP part (if utilizedas shown in, e.g., FIG. 8), and (c) a PSDU that is to be transmitted ona given sub-band. In this example, the legacy PLCP 721 consists of theSTF, LTF and SIG symbols modulated with an FFT size of 64 on a 20 MHzsub-channel and duplicated for every 20 MHz sub-channel if theimmediately preceding DL OFDMA PPDU 900 has a bandwidth wider than 20MHz. In one aspect, the partial HE PLCP part consists of the HE SIG-A801 using an FFT size of 64 and duplicated on all of the 20 MHzsub-channels that the immediately preceding DL OFDMA PPDU 900 consistsof. The payload section 726 includes PSDUs from participating STAs. APSDU is a payload for a given STA, and is modulated using an FFT size of256. Each participating STA forms a portion of the payload section 726with a PSDU in the sub-band (or sub-carrier) designated by theSUBCARRIERS_LIST of the immediately preceding DL OFDMA PPDU 900. In oneor more implementations, the MU ACK frame is formed without the partialHE PLCP part (e.g., the HE SIG-A 801).

In one or more aspects, a legacy PLCP 721 of a UL OFDMA PPDU 1000 (or aMU ACK frame) is formed as follows. All of the participating STAs thatsend an uplink frame that is in the form of a MU ACK frame, form thelegacy PLCP 721 (e.g., with an FFT size 64 for the bandwidth of 20 MHz).In some aspects, if the immediately preceding DL OFDMA PPDU 900 has abandwidth of 40 MHz, then the legacy PLCP 721 includes two identicalparts over two 20 MHz channels for a total bandwidth of 40 MHz. In otheraspects, if the immediately preceding DL OFDMA PPDU 900 has a bandwidthof 80 MHz, then the legacy PLCP 721 includes four identical parts for atotal bandwidth of 80 MHz. In still other aspects, if the immediatelypreceding DL OFDMA PPDU 900 has a bandwidth of 160 MHz or 80+80 MHz,then the legacy PLCP 721 includes eight identical parts for a totalbandwidth of 160 MHz.

The STE and LTF parts (also referred to as L-STE and L-LTF) of thelegacy PLCP 721 are formed according to the IEEE 802.11 specificationsfor HT and VHT compliant WLAN devices. The SIG part (also referred to asL-SIG) is encoded according to the 802.11 specifications for HT and VHTcompliant WLAN devices.

In some instances, a STA generates and transmits to the AP an MU ACKframe whose length corresponds or is identical to the length of a frameeliciting the response. For example, in one or more implementations, aL_LENGTH parameter in the TXVECTOR parameter associated with the MU ACKframe is set to a corresponding value indicated in a MUACK-L-LENGTHparameter of a HE control field of the immediately preceding DL OFDMAPPDU 900. In one aspect, L_LENGTH is a length of a PSDU of a UL OFDMAPPDU 1000. In one or more implementations, a MUACK-L-LENGTH parameter isindicated in another part of the immediately preceding DL OFDMA PPDU900, such as in the HE SIG-A 702 (FIG. 7) or the HE SIG-B 704 (FIG. 7)symbol(s) of the immediately preceding DL OFDMA PPDU 900. In someaspects, the L_LENGTH parameter in the TXVECTOR parameter associatedwith the MU ACK frame is set to a value corresponding to MUACKMaxLength.In one or more implementations, the MUACKMaxLength is a fixed valuecalculated based on a maximum possible length of a BA frame whenmodulated with MCS0 (e.g., BPSK at coding rate of ½) or MCS1 (e.g., QPSKat coding rate of ½). In some aspects, an AP (e.g., the wirelesscommunication device 111) announces the parameter MUACKMaxLength duringassociation. In other aspects, the AP announces the MUACKMaxLength inbeacon frames. In some other aspects, the MUACKMaxLength parameter isset to a predetermined value (or a fixed value a priori), such that allof the STAs that participate in forming the MU ACK frame are configuredto use identical values for the MUACKMaxLength parameter.

In some embodiments, the HE SIG-A 702 or the HE SIG-B 704 symbol(s) ofan immediately preceding DL MU PPDU carries an indication of the framelength of the multiplexed ACK/BA responses. In other embodiments, theindication of the frame length of multiplexed ACK/BA frames may be inthe form of a maximum duration of the payload of each ACK/BA frame asunits of time, such as units of 4 μs or 12 μs. In still otherembodiments, the indication of the frame length of multiplexed ACK/BAframes may be in the form of a maximum number of OFDM symbols that apayload of each ACK/BA frame takes. In yet other embodiments, theindication of the frame length of multiplexed ACK/BA frames may be inthe form of a multiplier of a unit interval, where the unit interval maybe based on the duration that the payload of an ACK frame takes(calculated with the same MCS as the MCS indicated for the givenmultiplexed ACK/BA responses). Note that the frame length of themultiplexed ACK/BA can be used to calculate MUACK-L-LENGTH.

In one aspect, the partial HE PLCP part of the MU ACK frame thatcontains the HE SIG-A 801, if present, is formed with an FFT size 64 forthe bandwidth of 20 MHz. In some aspects, only the first symbol of theHE SIG-A 801 symbols, sometimes referred to as HE SIG-A1, is present inthe partial HE PLCP part of the MU ACK frame. In some aspects, if theimmediately preceding DL OFDMA PPDU 900 has a bandwidth of 40 MHz, thenthe partial HE PLCP part has two identical parts for a total bandwidthof 40 MHz. In other aspects, if the immediately preceding DL OFDMA PPDU900 has a bandwidth of 80 MHz, then the partial HE PLCP part has fouridentical parts for a total bandwidth of 40 MHz. In still other aspects,if the immediately preceding DL OFDMA PPDU 900 has 160 MHz or 80+80 MHz,then the partial HE PLCP part can have eight identical parts for a totalbandwidth of 160 MHz.

In some instances, a STA generates and transmits to the AP an MU ACKframe whose channel bandwidth corresponds or is identical to the channelbandwidth of a frame eliciting the response. For example, the encodingof different fields of the HE SIG-A 801 may be with the same values thathave been indicated in the immediately preceding DL OFDMA PPDU 900.Particularly, parameters in the TXVECTOR parameter that are related toHE SIG-A 801 are set to values that are a priori known. However, achannel bandwidth (CH_BANDWIDTH) parameter in the TXVECTOR parameter isset to the same value as the CH_BANDWIDTH in the RXVECTOR parameterassociated with the immediately preceding DL OFDMA PPDU 900. In thisexample, the CH_BANDWIDTH parameter may represent the channel width (20MHz or 40 MHz) in which data is transmitted and the transmission format(e.g., HE PPDU format).

In one or more implementations, the fields in the HE SIG-A 801 areencoded with a fixed value that the AP announces during association. TheAP may announce the fixed value in beacon frames. Alternatively, the APmay announce the CH_BANDWIDTH parameter as fixed values such that STAsthat participate in forming the MU ACK frame use identical values forall of the fields in the HE SIG-A 801 symbols.

In some instances, a STA generates and transmits to the AP an MU ACKframe whose GI corresponds or is identical to the GI type of a frameeliciting the response. For example, in one or more implementations, informing a HE PLCP and/or PSDU part of a MU ACK frame, a participatingSTA (e.g., 210 or 211 of a STA) sets a GI_TYPE parameter in the TXVECTORparameter associated with the MU ACK frame carried in the HE PPDU format(with partial PLCP or preamble header as described above) to a valuecorresponding to a counterpart GI_TYPE parameter in the RXVECTORparameter of a frame eliciting the response. In some aspects, a STA(e.g., 210 or 211 of a STA) sets the GI_TYPE parameter in the TXVECTORparameter associated with a MU ACK frame carried in the HE PPDU format(with partial PLCP or preamble header as described above) to aLONG_GI_type, which indicates that short GI is not used in the packet.The GE_TYPE set to LONG_GI may be formed with an FFT size of 256. TheLONG_GI parameter may include values such as 1.6 ηs or 3.2 μs dependingon implementation.

In an UL OFDMA PPDU 1000, there may be another symbol that is called HELTF and its role is to assist the receiver to decode the payload. InFIGS. 7-10, HE LTF is not shown for brevity. STA creates the portion ofHE LTF that is associated with its assigned sub-band. HE LTF may be invarious short or long formats; however, all the STAs need to use thesame format for a single UL OFDMA PPDU. Hence, there are multipleembodiments in order to align the format of the HE LTF across all STAs.

In one or more implementations, all the STAs that respond with an ACK orBA frame in the form of an UL OFDMA PPDU can select the same HE LTFformat (i.e., long HE LTF or compressed HE LTF) and construct the HE LTFaccording to this format indication. In one embodiment, the format maybe indicated by the AP in the preceding DL OFDMA PPDU or DL MU PPDU (forexample in the HE SIG-B symbol of DL PPDU) and all the STAs pick thisindicated format to construct the HE LTF symbol of the UL OFDMA PPDU. Inanother embodiment, each STA can use the same HE LTF format as in thepreceding DL OFDMA PPDU or DL MU PPDU. In other words, if the precedingDL OFDMA PPDU or DL MU PPDU utilizes a long HE LTF format then each STAcan use a long HE LTF format to construct the HE LTF symbol in the ULOFDMA PPDU, and if the preceding DL OFDMA PPDU or DL MU PPDU utilizes acompressed HE LTF format then each STA can use a compressed HE LTFformat to construct the HE LTF symbol in the UL OFDMA PPDU. In anotherembodiment, the STAs may use a pre-determined format and construct theHE LTF symbol of UL OFDMA frame. There are multiple ways that suchpre-determined format may be communicated. For instance, the wirelessdevices may have such a pre-determined duration value defined/set duringmanufacture. In another instance, the AP may announce suchpre-determined format to each STA during association time. In anotherinstance, the AP may periodically announce such pre-determined format inBeacon frames. In another instance, the AP may use a combination ofabove methods to announce such pre-determined format and change thevalue if necessary and re-announce it to its associated STAs.

In some instances, a STA generates and transmits to the AP an MU ACKframe whose format, number of transmit chains, and/or coding typecorresponds or is identical to the format, number of transmit chains,and/or coding type of a frame eliciting the response. For example, insome aspects, a participating STA sets a FORMAT parameter in theTXVECTOR parameter associated with the UL OFDMA PPDU 1000 to a valuerepresenting HE while the STA sets a N_TX parameter in the TXVECTORparameter to one, among others. In this example, the N_TX parameterindicates the number of transmit chains. In some implementations, theSTA sets a FCC_CODING parameter in the TXVECTOR parameter to BCC_CODING(e.g., binary convolutional code encoding).

In one or more implementations, a STA sets a MCS parameter in theTXVECTOR parameter to a value of zero (e.g., MCS0). In some instances, aSTA generates and transmits to the AP an MU ACK frame whose MCS isidentical to the MCS of a frame eliciting the response. For example,some aspects, a STA sets the MCS parameter to a value corresponding to aMUACK-MCS parameter indicated by the AP in the immediately preceding DLOFDMA PPDU 900. The MUACK-MCS parameter may be indicated in theMUACK-MCS field of the HE control field (e.g., see HT control field 807)of the immediately preceding DL OFDMA PPDU 900. The AP may announce theMUACK-MCS parameter during association or in beacon frames. In someaspects, the AP sets the MUACK-MCS parameter to a fixed value a priori,such that all of the STAs that participate in forming the MU ACK frameuse identical values for the MUACK-MCS parameter.

In forming a PSDU part of the MU ACK frame, the sub-bands in the MU ACKframe that a participating STA uses to place associated PSDUs are basedon of the following examples. In some aspects, the STA uses identicalsub-bands from the immediately preceding DL OFDMA PPDU 900 that conveythe payload for the STA. In other words, a STA that intends to send anMU ACK frame sets the SUBCARRIERS_LIST of the TXVECTOR parameter for theMU ACK frame to the same value as in SUBCARRIERS_LIST of the RXVECTORparameter of the immediately preceding DL OFDMA PPDU 900. In thisexample, the SUBCARRIERS_LIST in the TXVECTOR parameter uniquelyidentifies the set of sub-carriers or equivalently the sub-bands thatthe STA uses.

FIG. 11 illustrates a schematic diagram of an example of a downlinkframe and an uplink frame for an OFDMA exchange among WLAN devices. Asimilar exchange as in FIG. 7 is illustrated in FIG. 11 except that theSTAs that receive payloads in the DL OFDMA PPDU 1100 do not all have thesame sub-band bandwidths.

In this case, the DL OFDMA PPDU 1100 includes a header section 710comprised of the legacy PLCP 701, the HE SIG-A 702, the HE STF/LTF 703and the HE SIG-B 704. The payload section 709 contains multiple PSDUpayloads where PSDU 1101 is associated with STA1. PSDU 1102 isassociated with STA2, PSDU 1103 is associated with STA3, PSDU 1104 isassociated with STA4, PSDU 1105 is associated with STA5 and PSDU 1106 isassociated with STA6. Here, each of the PSDUs 1101 and 1102 has asub-band with 20 MHz bandwidth while each of the remaining PSDUs1103-1106 has a respective sub-band with 10 MHz bandwidth.

The UL OFDMA PPDU 1120 includes a legacy PLCP 721 and a payload section726, The payload section 726 includes multiple ACK/BA payloads whereACK/BA payload 1121 is associated with STA1, ACK/BA payload 1122 isassociated with STA2, ACK/BA payload 1124 is associated with STA4 andACK/BA payload 1126 is associated with STA6. In this example, each ofthe ACK/BA payloads 1121, 1122, 1124 and 1126 has a sub-band with 20 MHzbandwidth.

In this example, the bandwidth of the DL OFDMA PPDU 1100 and thebandwidth of the subsequent MU ACK frame 1120 are the same; however, insome situations the bandwidths may be different. Not all of the STAs,which have an associated payload in the DL OFDMA PPDU 1100, respond withan ACK or BA frame, and some of STAs are not expected, or notinstructed, to respond since the corresponding ACK policy field in theQoS control field is not set to “Normal Ack or Implicit Block AckRequest.” In addition, the sub-bands, where the ACK/BA frames of theresponding STAs are placed within the payload section 726, are assignedto the STAs in a predetermined manner, which may be different from thereceived order of the sub-bands in the immediately preceding DL OFDMAPPDU 1100. For example, the set of sub-bands allocated for the ACK/BAframes of the participating STAs is signaled by indexing in theimmediately preceding DL OFDMA PPDU 1100.

In some aspects, this indication by the AP is generated and placed inthe HE SIG-A 702 or the HE SIG-B 704 symbols (part of the header 710) ofthe immediately preceding DL OFDMA PPDU 1100. In turn, the STA then setsthe SUBCARRIERS_LIST in the TX VECTOR parameter of the MU ACK framebased on the received indication. In such implementations, the STA isresponding with a MU ACK frame containing the ACK or BA frame of thatSTA. Such indexing may be signaled in HE SIG-B symbol of the precedingDL OFDMA PPDU, where the AP indicates the sub-band assignment within theDL OFDMA or DL MU frame and additionally indicates the sub-band indexfor the upcoming ACK or BA frame within the UL OFDMA frame. For theSTA(s) that no immediate ACK, or BA is expected, e.g., the QoS controlfield of the DL OFDMA PPDU is not set to “Normal Ack or Implicit BlockAck Request,” a reserved value such as sub-band zero is signaled,indicating that no sub-band is assigned.

It can be noted that the term MU ACK frame as used in the precedingsentence refers to an uplink frame generated by one STA, and such uplinkframe comprises a header (e.g., 721) and one PSDU (e.g., 1121), wherethe PSDU is associated with that STA and is associated with itscorresponding sub-band. Such uplink frame is in a “form” of a MU ACKframe but does not include PSDUs from other STAs. Thus, in such asituation, a MU ACK frame may refer to an uplink frame (comprising aheader and one PSDU) generated by one STA to participate in forming theultimate MU ACK frame (e.g., 1120) through RF combination. In anothercase, the term MU ACK frame may refer to the ultimate uplink frame(e.g., 1120), which is formed by aggregating and multiplexing multipleuplink frames from multiple STAs. In this latter case, the MU ACK frame(e.g., 1120) comprises a header and multiple PSDUs. Therefore, the termMU ACK frame can be understood in context, and it may refer to an uplinkframe generated by one STA to participate in forming the ultimate MU ACKframe, or it may refer to the ultimate uplink frame formed byaggregating multiple uplink frames generated by multiple STAs.

In one or more aspects, STAs transmit their respective uplink frames atthe same time, and these uplink frames are RF combined or aggregated toform a single, ultimate uplink frame (or a single, ultimate MU ACKframe). The AP receives and detects this single, ultimate MU ACK frame.

In some implementations, a STA obtains a MUACK-Sub-band parameter fromthe HE SIG-A 702 or HE SIG-B 704 symbols of the immediately preceding DLOFDMA PPDU 1100. In this regard, the STA then sets the SUBCARRIERS_LISTparameter in the TXVECTOR parameter of the MU ACK frame with a valuecorresponding to the obtained MUACK-Sub-band parameter. In suchimplementations, the AP (e.g., 210 or 215 of an AP) sets theMUACK-Sub-band field in the HE SIG-A 702 or the HE SIG-B 704 symbol ofthe DL OFDMA PPDU 1100 to a value that can represent the sub-bandallocation for that STA in a subsequent MU ACK frame. In otherimplementations, the STA (e.g. 210 or 211 of the STA) obtains theMUACK-Sub-band parameter from the RXVECTOR parameter of the immediatelypreceding DL OFDMA PPDU 1100.

In one or more implementations, if the AP (e.g., 210 or 211 of an AP)does not set the ACK policy field in the QoS control field to “NormalAck or Implicit Block Ack Request,” then the AP (e.g., 210 or 215 of anAP) sets the MUACK-Sub-band field in the HE SIG-A 702 or HE SIG-B 704symbol of the DL OFDMA PPDU 1100 to an invalid or reserved value, whichimplies that the receiving STA does not have a sub-band allocated forsending an ACK or BA in the next MU ACK frame.

On the other hand, if the AP (e.g., 210 or 211 of an AP) sets the ACKpolicy field in the QoS control field to “Normal Ack or Implicit BlockAck Request” of the frame (e.g., PSDU payload) that is carried for aSTA, then the AP (e.g., 210 or 215 of an AP) sets the MUACK-Sub-bandfield in the HE SIG-A 702 or the HE SIG-B 704 symbol in the DL OFDMAPPDU 1100 to a valid value, which represents a sub-band having beenallocated for the ACK or BA frame of that STA.

In one or more implementations, the MUACK-Sub-band parameter included inthe HE SIG-A 702 or the HE SIG-B 704 symbol of the DL OFDMA PPDU 1100,which may carry respective payloads intended for two STAs, is not set tothe same value unless the ACK policy field in the QoS control field ofthe associated frames carried to the two STAs are different than “NormalAck or Implicit Block Ack Request.” The size of the MUACK-Sub-band fieldmay vary depending on implementation, but the size may be set to indexall of the allocated sub-bands within a given PPDU bandwidth. Forinstance, for sub-bands where each sub-band has a bandwidth of 5 MHz,the MUACK-Sub-band field has 2-bit length for PPDUs with 20 MHzbandwidth, has 3-bit length for PPDUs with 40 MHz bandwidth, has 4-bitlength for PPDUs with 80 MHz bandwidth, and has 5-bit length for PPDUswith 160 MHz bandwidth.

In some aspects, an implicit indication is used instead of theMUACK-Sub-band parameter to inform each STA which sub-band has beenassigned to that STA for placing a corresponding ACK/BA frame.

In one aspect, an AP may identify the number and position of thesub-bands that are allocated for MU ACK frame transmission. Thisimplicit indication may be generated within the HE SIG-B 704 field ofthe DL OFDMA PPDU 1100 (by, e.g., a PHY processor 215), where theindication relates to an identification of the number of sub-bands. Notethat actual location of the sub-bands may be known a priori by the APand the STAs, given the bandwidth of the MU ACK frame. For instance, theMU ACK frame may have a 20 MHz bandwidth with nine sub-bands (where eachsub-band has a 2 MHz bandwidth), or four sub-bands (where each sub-bandhas a 4 MHz bandwidth). In this regard, so long as the number ofacknowledgment frames (which from the above example is either 9 or 4),or alternatively the bandwidth of acknowledgment sub-bands, is specifiedby the AP (e.g., by its baseband processor) in the DL OFDMA PPDU 1100,the STAs can be notified of the location of the sub-bands andcorresponding order.

In some aspects, the order may be determined by some convention such asthe sub-band with lowest frequency (or smallest sub-carrier or sub-bandidentification) is assigned index 1, and other sub-bands have an indexincremented from index 1. For instance, the MU ACK frame has foursub-bands and, based on a predetermined convention between the AP andSTAs, the top sub-band is indexed 1, and the next sub-band is indexed 2,etc., and the bottom sub-band is indexed 6.

Alternatively, the number of sub-bands for ACK/BA frames may be known apriori. For instance, if the AP expects to receive the MU ACK frame witha 20 MHz bandwidth, and each sub-band is expected to have a respective 2MHz bandwidth, then such a priori convention between the AP and the STAsimplicitly identifies the number of sub-bands for ACK/BA multiplexing.Similarly, an implicit order of the sub-bands may be understood betweenthe AP and the STAs.

Once the number of the sub-bands for ACK/BA multiplexing and an inherentorder of the sub-band are known between the AP and the STAs, then eachSTA can select the ACK/BA sub-band that has the same index/order as theindex/order assigned to the payload of the STA via the HE SIG-B 704 ofthe preceding DL OFDMA PPDU 1100. For instance, the MU ACK frame hasfour sub-bands where the sub-bands from top to bottom are indexed 1, 2,3 and 4 respectively. The STA whose sub-band assignment in the precedingDL OFDMA PPDU 1100 is listed first can use the ACK/BA sub-band withindex 1 in the MU ACK frame. The STA whose sub-band assignment in thepreceding DL OFDMA PPDU 1100 is listed second can use the ACK/BAsub-band with index 2 in the MU ACK frame. The STA whose sub-bandassignment in the preceding DL OFDMA PPDU 1100 is listed third can usethe ACK/BA sub-band with index 3 in the MU ACK frame. Finally, the STAwhose sub-band assignment in the preceding DL OFDMA PPDU 1100 is listedfourth can use the ACK/BA sub-band with index 4 in the MU ACK frame.

In another embodiment, each STA uses one of the sub-bands among the setof sub-bands that is assigned to the STA in the preceding DL OFDMA PPDU.For instance, each STA may use the first sub-band with a given bandwidth(e.g., 2 MHz, or 4 MHz or 5 MHz) from the sub-bands that has beenassigned to the STA in the preceding DL OFDMA PPDU. In anotherembodiment, each STA may use the first 2 MHz sub-band from the sub-bandsthat has been assigned to the STA in the preceding DL OFDMA PPDU. Inanother embodiment, each STA may use the first 4 MHz sub-band from thesub-bands that has been assigned to the STA in the preceding DL OFDMAPPDU, and if a STA has a narrower sub-band in the preceding DL OFDMAPPDU, then the STA chooses the same sub-band as in the preceding DLOFDMA sub-band. The AP can either indicate that the 2 MHz or 4 MHzsub-band designation for ACK and BA frames within a UL OFDMA PPDU, or inthe preceding DL OFDMA PPDU, or broadcasted within Beacon frames, or leteach STA know about such designation during association time.

Note that while the bandwidth of the UL OFDMA PPDU 1120 may be the sameas the DL OFDMA PPDU 1100, the bandwidth of the UL OFDMA PPDU 1120 maybe narrower than the bandwidth of the DL OFDMA PPDU 1100. For example,while a DL OFDMA PPDU 1100 has a bandwidth of 80 MHz (e.g., primary 40MHz and secondary 40 MHz), the UL OFDMA PPDU 1120 may have a bandwidthof 40 MHz only (e.g., primary 40 MHz only). In some aspects, the APestablishes the bandwidth of the MU ACK frame in advance such that theparticipating STAs are notified of the bandwidth prior to formation ofthe MU ACK frame. In some examples, the bandwidth of the MU ACK framemay be fixed to a bandwidth of 20 MHz irrespective of the bandwidth ofthe DL OFDMA PPDU 1100. In other examples, the bandwidth of the MU ACKframe may be fixed to 40 MHz when the DL OFDMA PPDU 1100 has a bandwidthof 40 MHz or more.

In one or more implementations, the indication of the bandwidth for theMU ACK frame may be performed in one of the following ways: (a) the ULbandwidth may be identified by an indication to all of the STAs eitherin beacon frames or during association time, or (b) the UL bandwidth maybe identified in each DL OFDMA frame within the HE SIG-A 702 or the HESIG-B 704. In some implementations, where the bandwidth for all of thesub-bands assigned to ACK or BA frame have been identified to be thesame, the total number of the sub-bands for ACK/BA multiplexing is givenas part of the indication.

In some implementations, the AP (e.g., 210 or 211 of the AP) partitionsthe sub-bands for a MU ACK frame such that multiple relatively narrowsub-bands are assigned to ACK frames while multiple relatively widersub-bands are assigned to BA frames. For example, a sub-band for an ACKframe is narrower than a sub-band for a BA frame. This is due to thefact that the ACK frame is typically shorter than a BA frame.Information relating to such partition may be announced by the AP duringassociation time or in Beacon frames. For instance, in a MU ACK framewith 20 MHz bandwidth, the AP may assign two sub-bands (each sub-bandwith 4 MHz bandwidth) for BA frames, and five sub-bands (each sub-bandwith 2 MHz bandwidth) for ACK frames. Such partitioning may allow formore efficient MU ACK frame transmission.

In the above embodiments, the AP assigns sub-bands to the STAs (thathave a payload addressed in a DL MU frame and are expected to send anACK or BA frame in the immediately following MU ACK) in an implicit wayso that the STAs place their ACK or BA frames in a unique sub-band (withno chance that another STA picks the same sub-band, hence no chance ofcollision). However, in the above embodiment, the bandwidth of thesub-band assignment for any ACK frame is the same as any BA frame. Sincethe ACK frames are typically shorter than BA frames, one outcome ofassigning the same bandwidth to these frames causes the STAs that aresending an ACK frame to pad their ACK frame (where padding happens inMAC and/or PHY entities) enough so that the resulted ACK frame has thesame length as the BA frame. In another embodiment, the above-mentionedindication may be altered so that different bandwidths are assigned toACK and BA frames. Such indication may work as follows: First the APassigns abase bandwidth that is applicable to all STAs. The basebandwidth may be assigned to a sub-field denoted as ACKBABaseBW. In thisembodiment those STAs that are going to send an ACK frame use the samebase bandwidth; however, those STAs that are going to send a BA frameuse twice that bandwidth. For instance, the AP may set ACKBABaseBW to 2MHz (26-tone sub-band or RU), in which case the STAs that are going tosend an ACK frame can use sub-bands with 2 MHz bandwidth and the STAsthat are going to send a BA frame can use sub-bands with 4 MHz bandwidth(52-tone RU). To specifically indicate this bandwidth assignment, the APcan assign a sub-field to each STA which is denoted by ACKBW. In someembodiments this sub-field is binary, where the TRUE value indicatesthat the STA intends to send an ACK frame, hence the STA can use asub-band with bandwidth ACKBABaseBW. If ACKBW is set to a FALSE value,the AC/BW sub-field then indicates that the STA intends to send a BAframe, hence the STA can use a sub-band with bandwidth twice that ofACKBABaseBW. Since the ACKBW sub-field for each STA appears in the HESIG-B field of the DL MU frame, each STA gathers the value ACKBW for allthe STAs and knows what is the bandwidth used by each STA. Hence,combining that with the order of appearance of the STA sub-band info inthe HE SIG-B, each STA can uniquely identify which sub-band to select inorder to place its ACK or BA frame.

For instance, the MU ACK frame may have a 20 MHz bandwidth with ninesub-bands each with a 2 MHz bandwidth, or four sub-bands each with s 4MHz bandwidth. In this example, the AP sets ACKBABW to 2 MHz, 6 STAshave payloads in the DL MU frame, and the third and fourth STAs areexpected to respond with a BA frame (hence the AP sets the ACKBWsub-field for these STAs to a FALSE value), while the remaining STAs areexpected to respond with an ACK frame (hence the AP sets the ACKBWsub-field for these STAs to a TRUE value). Given the above settings, andgiven that each STA reads the ACKBW of all the STAs, then the followingis the sub-band orders that the STAs select (note that the reference ofsub-bands to be chosen for ACK/BA is priori known and for instancestarts from the highest-frequency sub-band or from lowest-frequencysub-band depending on implementation):

-   -   The first STA whose sub-band info appears in the HE SIG-B field        chooses the first 2 MHz sub-band (given that ACKBW is set to        TRUE)    -   The second STA whose sub-band info appears in the HE SIG-B field        chooses the second 2 MHz sub-band, given that ACKBW is set to        TRUE, and prior ACKBW values are: TRUE    -   The third STA whose sub-band info appears in the HE SIG-B field        chooses a 4 MHz sub-band (i.e., the third and fourth 2 MHz        sub-band), given that ACKBW is set to FALSE, and prior ACKBW        values are: TRUE, TRUE    -   The fourth STA whose sub-band info appears in the HE SIG-B field        chooses a 4 MHz sub-band (i.e., the fifth and sixth 2 MHz        sub-band), given that ACKBW is set to FALSE, and prior ACKBW        values are: TRUE, TRUE, FALSE    -   The fifth STA whose sub-band info appears in the HE SIG-B field        chooses a    -   2 MHz sub-band (i.e., the seventh 2 MHz sub-band), given that        ACKBW is set to TRUE, and prior ACKBW values are: TRUE, TRUE,        FALSE, FALSE    -   The sixth STA whose sub-band info appears in the HE SIG-B field        chooses a 2 MHz sub-band (i.e., the eighth 2 MHz sub-band),        given that ACKBW is set to TRUE, and prior ACKBW values are:        TRUE, TRUE, FALSE, FALSE, TRUE.    -   In above, each prior TRUE value of ACKBW counts as one (order of        sub-bands with ACKBABW=2 MHz) and each prior FALSE value of        ACKBW counts as two (order of sub-bands with ACKBABW=2 MHz,        e.g., twice that bandwidth hence 4 MHz).

In the above embodiment, ACKBW is a binary sub-field and takes twovalues. However, in general, ACKBW may take more than two values. Forinstance, a 2-bit representation of ACKBW may be structured as follows:value 00 indicates that there is no sub-band assigned to the DL payload,value 01 indicates that the sub-band assigned to the DL payload has thesame bandwidth as indicated in ACKBABW, value 10 indicates that thesub-band assigned to the DL payload has twice the bandwidth as indicatedin ACKBABW, and value 11 indicates that the sub-band assigned to the DLpayload has three times the bandwidth as indicated in ACKBABW, Similarto the example described above, each STA that has a payload maydetermine its sub-band by observing the ACKBW values for all the STAswhose DL payload has been indicated earlier in the HE SIG-B of the DL MUframe. Note that the value 00 for ACKBW as described above is used whenthe ACK Policy field in the QoS control field in a DL payload is set to“No Ack” or “Block Ack.”

With respect to FIGS. 7-11, it is possible to convey the necessaryinformation for carrying the information for ACK/BA responses for allSTAs in a separate frame that is assigned to a sub-band. Such frame isdenoted as a Trigger frame and it has information such as: the durationof the MU ACK (or the multiplexed ACK/BA responses as shown in FIGS.7-11), the sub-band assignments for each of the payloads, the MCS/NSSfor each of the STAs, etc). The presence of a Trigger frame may beindicated in HE SIG-A or HE SIG-B as well as the sub-band of the Triggerframe. All the STAs that have a payload in the DL MU frame first decodeand interpret HE SIG-A and HE SIG-B and find out whether there is aTrigger frame and then the STAs process and decode their own payload (asindicated in HE SIG-B) as well as the Trigger frame. Then the STAs findout from the Trigger the above-mentioned details that they need in orderto multiplex their ACK or BA frame in the subsequent MU ACK frame. Insome embodiments, as long as the AP indicates there is a Trigger frameinside the DL MU frame, all the STAs that have captured the DL MU framecan process and decode the Trigger frame and can find out whether thereis any assignment for the STA. This means that a STA that has a DLpayload can process and decode the Trigger frame (in which case theTrigger frame indicates the information to multiplex their ACK/BAresponse), as well as the STAs that do not have payloads can process anddecode the Trigger frame which case the Trigger frame indicates theinformation to multiplex a data, management, or control frame).

FIG. 12 illustrates a schematic diagram of an example of a downlinkframe with a trigger frame in a payload of the downlink frame and anuplink frame. In this case, a DL OFDMA PPDU 1200 includes a headersection 1209 comprised of the legacy PLCP 1201 (including the HE SIG-A),the HE SIG-B 703 and the HE STF/LTF 704. The payload section 1208contains multiple PSDU payloads where PSDU 1204 is associated with STA1,PSDU 1205 is associated with STA2, PSDU 1206 is associated with STA3 andPSDU 1207 is associated with STA4. Here, each of the PSDUs 1205 and 1207has a sub-band that is larger than the sub-band of each of the remainingPSDUs 1204 and 1206.

The UL OFDMA PPDU 1220 includes a legacy PLCP 1221 (with the HE SIGsymbol) and a payload section 1226. The payload section 1226 includesmultiple ACK/BA payloads where BA payload 1224 is associated with STA1.BA payload 1223 is associated with STA2, ACK payload 1225 is associatedwith STA3 and ACK payload 1222 is associated with STA4. In this example,each of the ACK payloads 1222 and 1225 has a sub-band with a bandwidththat is smaller than the sub-band bandwidths of each of the BA payloads1223 and 1224.

In some embodiments, the above-mentioned Trigger frame appears in thesame sub-band as the DL payload (e.g., as an MPDU within the AMPDU)where the Trigger frame is essentially a single-STA Trigger frame. TheTrigger frame provides the above-mentioned information (e.g., theduration and the sub-band assignment, etc. for the same STA that has thepayload in that DL sub-band. In some embodiments, the Trigger frame(e.g., 1216) appears as the first MPDU inside the A-MPDU after which thedata/management MPDU follows. In FIG. 12, the Trigger frame/MPDU isshown as a gray box inside each DL payload in each sub-band. The Triggerframe may identify one or more resource units (or sub-bands) assigned toeach of the STAs for transmitting its uplink frame. A STA (e.g., STA1)that receives and processes the DL MU frame (e.g., 1200) may determinewhether there is a payload in a sub-band destined to the STA (e.g.,1204). The STA first decodes the Trigger frame (e.g., 1216) and when itobtains the content of the Trigger frame, the STA prepares for sendingthe ACK or BA (e.g., BA 1224) or any other appropriate response frame inthe sub-band that is indicated in the Trigger frame (and according toother properties mandated by the Trigger frame such as theduration/length of the ACK/BA frame). Then the STA processes and decodesthe remaining MPDUs in the payload (e.g., 1204). As described herein,the Trigger frame may thus include scheduling information for a PPDUthat carries an immediate acknowledgment. Note that in some embodiments,the STA may perform above-mentioned processing in parallel.

In some aspects, if a BA frame (e.g., 1223, 1224) is sent as animmediate response to either an implicit BA request that was carried inan HE OFDMA PPDU (e.g., 1200), the MU ACK frame (that contains the BAframe) can be carried in a HE PPDU with the setting as described above.The rate and bandwidth of the BA is selected as described above usingCODING, MCS, GI parameters of the RXVECTOR parameters of the HE DL OFDMAPPDU in order to set CODING, MCS, GI parameters of the TXVECTORparameters of the MU ACK frame.

In some aspects, if an ACK frame (e.g., 1222, 1225) is sent as animmediate response to either an implicit BA request that was carried inan HE OFDMA PPDU (e.g., 1200), the MU ACK frame can be carried in HEPPDU with the setting as described above. The rate and bandwidth of theBA is selected as described above using CODING, MCS, GI parameters ofthe RXVECTOR parameters of the HE DL OFDMA PPDU to set CODING, MCS, GIparameters of the TXVECTOR parameters of the MU ACK frame.

While receiving an MU ACK frame transmitted in the HE PPDU format withdetails described above, the AP (e.g., 210 or 211 of the AP) uses theRXVECTOR parameter SUBCARRIERS_LIST to identify which STA has respondedwith ACK and BA frames. The MAC entity (e.g., the MAC processor 211 orthe MAC software processing unit 212 and/or the MAC hardware processingunit 213 of the MAC processor 211) compares the RXVECTOR parameterSUBCARRIERS_LIST with the TXVECTOR parameter SUBCARRIERS_LIST of thepreceding HE OFDMA PPDU and identifies which of the STAs hasparticipated in forming the MU ACK. Specifically for ACK frames, the APdoes not know which STA has sent the ACK frame since there is no TAfield in the received ACK frame (e.g., ACK frame only has RA address).However, in some embodiments where the SUBCARRIERS_LIST of the TX VECTORof a HE OFDMA PPDU and the SUBCARRIERS_LIST of the TXVECTOR of theimmediately following MU ACK are the same for each STA that receives apayload in the HE OFDMA PPDU and participates in forming the MU ACKframe, the AP can compare to verify the presence of the SUBCARRIERS_LISTin the RX VECTOR of the received MU ACK frame. If the BA or ACK frame isnot present in the given SUBCARRIERS_LIST of the received MU ACK frame,the AP infers that the STA with the given SUBCARRIERS_LIST (in the DLOFDMA and MU ACK exchange) has not sent an ACK or BA frame. If a BA orACK frame is present in the given SUBCARRIERS_LIST of the received MUACK frame, and if the frame is an ACK frame, then the AP can furtherinfer which STA has sent the ACK frame (see FIG. 10).

While receiving an MU ACK frame transmitted in the HE PPDU format withdetails described above, an AP transfers a payload (DATA) from a PHY toa local MAC entity with the below PHY-DATA.indication primitive. Theprimitive provides the following parameter: PHY-DATA.indication, (DATA,USER_INDEX). The DATA parameter may be an octet of value X′00′ to X′FF′.The USER_INDEX parameter (typically identified as u for a HE STA) ispresent for a HE UL OFDMA PPDU or a HE UL MU PPDU, and indicates theindex of the user in the RXVECTOR to which the accompanying DATA octetapplies. Otherwise, USER_INDEX parameter is not present. ThePHY-DATA.indication primitive is generated by a receiving PHY entity(e.g., the PHY processor 215 or the RX signal processing unit 290 of thePHY processor 215) to transfer the received octet of data to the localMAC entity. The time between receipt of the last bit of the lastprovided octet from the WM and the receipt of the PHY-DATA.indicationprimitive by the MAC entity is aRxPHYDelay. The effect of receipt ofthis primitive by the MAC is unspecified.

FIG. 13 illustrates an example of an extended control field 1320 in a HTcontrol field 1300 of a data frame. For convenience, the extendedcontrol field 1320 is sometimes referred to as an HE Control extendedsubfield/field or an HE control subfield/field.

In some embodiments, an AP may use the QoS control field in the MACheader of each MPDU and an extended HT control field (denoted as HEControl Extension (HECE) in the HT control field) in a DL payload tonotify a STA (that has a payload in the DL MU frame) about the sub-bandthat the STA can use to place its ACK or BA frame in the immediatelymultiplexed-ACK/BA frame. As described herein, the HT control field 1300may be located in a MAC header of a trigger MPDU within a payload of amulti-user downlink frame (e.g., DL OFDMA PPDU or DL MU MIMO PPDU). Insome aspects, the trigger MPDU is a control frame that carries the HTcontrol field 1300 in a payload of the trigger MPDU. In other aspects,the HT control field 1300 is a High Efficiency control field within theMAC header of the trigger MPDU.

In one or more implementations, a STA may use both the QoS control fieldand the HT control field 1300 (having the HECE subfield 1320) to conveyinformation relating to the queue size and/or frequency selectivitystatus of the STA to its associated AP. The HT control field 1300 mayinclude a HE control extension indication (HECEI) field 1311, which maybe located in an HT control middle section 1310 of the HT control field1300. The HT control field 1300 includes the HECE subfield 1320.

Still referring to FIG. 13, in one aspect, if the HECEI field is set toone, then the HECE subfield 1320 exists; otherwise the HECE does notexist. In one or more implementations, the HECE subfield 1320 carriesone or more of the following information: ACK/BA sub-band, LTF SetIndex, ULDL, bandwidth, sub-band resolution, length information, MCS andNSS per sub-band (or per each of the sub-bands with the mentionedsub-band resolution), buffer-status or queue size per TID, oralternatively, buffer-status or queue size per AC, quality indicator ofthe full-hand or sub-bands, and sub-channel medium status report. TheHECE subfield 1320 may also include an identification subfield toindicate what subset of the listed subfields in 1320 are carried in aspecific instance of an HECE in a frame. For each payload in a DL MUframe, an AP may use HECE in the MAC header and fill the designated“ACK/BA sub-band(s)” field with the sub-band(s) that the STA may use tosend its ACK or BA frame. The “ACK/BA sub-band(s)” field in HECE may beinterpreted as follows: it is present in MAC headers of the MPDUs thatare conveyed in a DL MU PPDU. If present, it indicates the sub-band orsub-bands that the AP assigns to the STA in order to place its ACK/BAframe in the multiplexed or MU ACK/BA frame in uplink direction. Asub-band may be referred to as a resource unit. An AP may schedule whichSTAs to use which sub-bands; hence, an AP may provide uplink multi-userresponse scheduling information. As described herein, the HECE subfield1320 may include scheduling information for a trigger-based PPDU thatcarries an immediate acknowledgment. Note that the HECE sub-field 1320may have additional sub-fields such as “Number of sub-bands,” wherecollectively these sub-fields explicitly identify all the sub-bands thatthe STA intends to use to place its ACK/BA frame in the UL multiplexedACK/BA frame. The “sub-channel medium status report” in the HECEsubfield 1320 indicates the status of each of the 20 MHz sub-channelsthat the STA senses before sending a frame that carries the HT controlfield 1300 and HECE subfield 1320 (or a response frame to an elicitingframe that may request the sub-channel medium status). The frame mayoccupy the Primary 20 MHz channel, or it may occupy a sub-band or RUwithin a 20 MHz sub-channel (in an UL MU PPDU). Depending on theimmediately preceding frame that elicits the response frame and thebandwidth of the eliciting frame, the STA may perform carrier sensing(CS) or energy detection (ED) on one or more 20 MHz sub-channels thatthe eliciting frame occupies after which the STA reports the mediumstatus of each of the sensed 20 MHz sub-channels within the HECEsubfield 1320 of the response frame. The medium status report mayindicate whether the medium is IDLE or BUSY as defined in an IEEE 802.11specification, or may indicate whether the signal or energy that issensed in each 20 MHz sub-channel is less than a specified threshold(e.g., an OBSS_PD threshold, or one or more thresholds indicated in theeliciting frame, for instance one or more thresholds from the set of{−82 dBm, −72 dBm, −62 dBm, . . . }). In an embodiment, one or moresub-channel medium status reports may be reported for each 20 MHzsub-channel, where each report corresponds to a predetermined threshold(e.g., a report indicates whether the signal or energy that is sensed ina 20 MHz sub-channel is less than a first threshold and another reportindicates whether the signal or energy that is sensed in the same 20 MHzsub-channel is less than a second threshold. In another embodiment, thebasis for sub-channel medium status might be a narrower or widerbandwidth than 20 MHz, either as a pre-determined bandwidth basis, or asan indicated bandwidth basis in the eliciting frame. In anotherembodiment, the basis for sub-channel medium status report is Primary 20MHz, Primary 40 MHz, Primary 80 MHz, and Secondary 80 MHz where a STAreports the status of one or more of these sub-channels. In an example,an AP may send a trigger frame to a set of STAs. Within the triggerframe the AP may request each STA to send its buffer status in thefollowing UL MU PPDU and/or the AP may request each STA to sendsub-channel medium status. Each responding STA then sends its bufferstatus (per AC or per TID or for all TIDs) in a HE Control (HEC) fieldof the response frame and/or sends the sub-channel medium status (foreach 20 MHz sub-channel) within the same HEC field or in an HEC field ofanother MPDU within the same response frame (or both reports carried inthe HEC field of a QoS Null frame). In an embodiment, a responding STAmay send unsolicited sub-channel medium status (for each 20 MHzsub-channel) within the HEC field of an MPDU of the same response frame(or carried in HEC field of a QoS Null frame). In above example, the APuses the sub-channel medium status reports from each STA to schedule theupcoming DL SU or MU frames or UL MU frames. In an embodiment, the APdoes not schedule any DL payload or schedule any UL transmission on oneor more 20 MHz sub-channels for a STA, if the STA indicates unfavorablemedium status in those sub-channels (e.g., if the report indicates aBUSY status, or if the STA indicates the energy level on thesub-channels is larger than a specified threshold).

As indicated above, length information may be indicated in the HECEsubfield 1320. This length information may be utilized by the receivingSTA to indicate the length of the response frame (e.g., the UL MUframe). For example, in one or more implementations, a L_LENGTHparameter in the TXVECTOR parameter associated with the MU ACK frame isset to a corresponding value indicated in a MUACK-L-LENGTH parameter ofa HE control field of the immediately preceding DL PPDU. In one aspect,L_LENGTH is a length of a PSDU of a UL OFDMA PPDU. In some aspects, theL_LENGTH parameter in the TXVECTOR parameter associated with the MU ACKframe is set to a value corresponding to MUACKMaxLength. In one or moreimplementations, the MUACKMaxLength is a fixed value calculated based ona maximum possible length of a BA frame when modulated with MCS0 (e.g.,BPSK at coding rate of ½) or MCS1 (e.g., QPSK at coding rate of ½). Insome aspects, an AP announces the parameter MUACKMaxLength duringassociation.

Note that one or more of the above-identified subfields in the HECEsubfield 1320 are optional, or may appear based on some indication.Depending on an indicator that appears at a given location, e.g., thebeginning of the HECE subfield 1320, the reported parameters in theremaining portion of the HECE subfield 1320 is indicated, e.g., the HECEsubfield 1320 includes a subset of the attributes listed above. Forexample, with a reserved value appearing in the indicator, the queuesize and/or buffer status per AC or all ACs is reported in the HECEsubfield 1320. In another example, with another reserved valuesappearing in the indicator, an additional indication of the queue sizeper AC or per TID is reported in the HECE subfield 1320. In anotherexample, with another reserved value appearing in the indicator, MCS,NSS or some quality indicator (such as SNR or RSSI) is reported in theHECE subfield 1320. In another example, with another reserved valueappearing in the indicator, duration or sub-band assignment of asubsequent response frame is reported in the HECE subfield 1320.Accordingly, the indicator value in the HECE subfield 1320 indicates theparameters in the HECE subfield 1320.

When the ULDL, subfield in the HECE subfield 1320 is set to one, theindicated values for the MCS and NSS per sub-band in the HECE subfield1320 are values that the STA intends to employ for each specifiedsub-band in the next (or one or more subsequent) UL OFDMA PPDUs or ULMIMO PPDUs.

The values provided in the HECE subfield 1320 may be used when an STAintends to participate in forming an upcoming UL OFDMA PPDU or UL MUMIMO PPDU, and the STA intends to notify the AP on which MCS and NSSvalues are intended to be used in the specified sub-bands provided thatthe AP creates an assignment for the STA in any of the sub-bands. Inthis case, the MCS and NSS values may be used by the AP in creating theSTA assignment, sub-band assignment, and spatial-stream (SS) assignmentof the one or more subsequent UL OFDMA PPDUs or UL MIMO PPDUs. In someaspects, if the AP assigns more than one sub-band with the specifiedresolution to the STA in the next UL OFDMA PPDU or UL MU MIMO PPDU, thenthe STA may use the more robust MCS and NSS values across two or moresub-bands.

When the ULDL subfield in the HECE subfield 1320 is set to zero, theindicated values in the HECE subfield 1320 are recommended valuesdirected to the MCS and NSS or some other quality indicators (such asRSSI or SNR) per sub-band for the AP to use in the next (or one or moresubsequent) DL OFDMA PPDUs. For example, the MCS and NSS values may be arecommendation to the AP on which MCS or NSS values to use for the nextDL OFDMA or DL MU MIMO PPDUs. The recommendation of the MCS and NSSvalues may be interpreted by the AP as solicited or unsolicited valuesby the AP, depending on the other subfields in the HT control field1300. In some aspects, the AP may determine not to include the STA in anext (or one or more subsequent) UL MEMO PPDU or UL OFDMA PPDU based oninformation reported in the HECE subfield 1320, particularly withrespect to the MCS, NSS and/or queue size values, irrespective of theULDL value.

In some embodiments, in the MU (or multiplexed) ACK/BA frame thatimmediately follows a DL MU PPDU, the AP that sends the DL MU PPDU maynot assign all the sub-bands to the expecting ACK/BA frames. When the APleaves some sub-bands unassigned, the AP identifies the unassignedsub-bands in the HE SIG-B of the DL MU PPDU, along with some otherattributes of the MU ACK/BA frame such as its duration. Other STAs thathave received the DL MU PPDU and decoded the HE SIG-B section of theframe successfully can realize what sub-bands are going to be availablein the upcoming MU ACK/BA frame that immediately follows the DL MU PPDU.These STAs can be allowed to send control/management frames (such asUplink-Request frame, PS-Poll frame, or even a delayed BA from anearlier exchange with AP) or data frame (which may be a QoS null framethat carries queue size and may have the HECE sub-field 1320) in theunassigned sub-band only if the duration of the frame fits the specifiedduration of the MU ACK/BA frame.

In other embodiments, the AP that sends the DL MU PPDU may not assignall the sub-bands to the expecting ACK/BA frames and some sub-bands maybe assigned to other STAs from which the AP expects to receive a frame(this may be based on prior exchanges the AP had with the STA, based onwhich the AP expects a short data frame or some control or managementframes from the STA). The AP indicates the unassigned sub-bands in theHE SIG-B of the DL MU PPDU, along with some other attributes of the MUACK/BA frame such as the AID/PAID of the STA assigned with a sub-band bythe AP, the duration of the MU ACK/BA frame, etc. The STA whose AID/PAIDappears in an MU ACK/BA frame (but did not have a DL payload in theimmediately preceding DL MU frame) can be allowed to sendcontrol/management frames (such as Uplink-Request frame, PS-Poll frame,or even a delayed BA from an earlier exchange with AP) or data frame(which may be a QoS Null frame that carries queue size and may have theHECE sub-field 1320) in the assigned sub-band only if the duration ofthe frame fits the specified duration of the MU ACK/BA frame.

It some embodiments, an MU ACK is invoked for frames other than DL MUframes. For instance, a MU ACK response may be invoked as a response toa frame that is sent as multicast frame where multiple STAs receive thesame payload from another STA, e.g., an AP. In such cases, while the DLpayload is the same for all (hence the reason sent in multicast format),the STAs may each have a different experience on whether they havedecoded the MPDU or MPDUs successfully. While it is more robust if eachSTA sends its ACK and BA frames in response to multicast frames, it ismore efficient if the STAs multiplex their ACK or BA frames with thesame principle as described above. Note that since the payload for allthe STAs that receive a multicast frame is the same, hence it isexpected that either all the STAs respond with ACK frame (if themulticast payload has only one MPDU) or all the STAs respond with BAframe (if the multicast payload has multiple MPDUs).

In some embodiments, after a multicast frame, a MU block acknowledgmentrequest (BAR) frame follows where the AP identifies the list of STAsthat expects an acknowledgment response, and assigns to each STA asub-band to be used for multiplexing their ACK or BA response. Note thatthe list of STAs identified in the MU BAR may include all the STAs thatbelong to the multicast group, or may include a subset of the STAs thatbelong to the multicast group. A sub-band may be referred to as aresource unit. In one or more embodiments, multicast transmission may beassociated with group-cast with retry (GCR) service, and a multicastgroup may refer to a GCR group.

In some embodiments, after a multicast frame, a MU BAR frame followswhere the AP identifies the list of STAs that expects an acknowledgmentresponse. Note that the list of STAs identified in the MU BAR mayinclude all the STAs that belong to the multicast group, or may includea subset of the STAs that belong to the multicast group. The AP alsoidentifies the bandwidth (in a field denoted by AcknowledgmentBW) thatcan be used for multiplexing the ACK or BA response. In this embodiment,the AP does not identify the specific sub-bands for each STA. Rather,given the value of AcknowledgmentBW, each STA is implicitly assignedwith a sub-band (among all the sub-bands with bandwidthAcknowledgmentBW) that has the same order as the order of the STA in theabove-mentioned list of the STAs (e.g., if the identification of the STAappears in the nth order in the list of the STAs in the MU BAR frame,then the STA chooses the sub-band with bandwidth AcknowledgmentBW thathas the order ‘n’).

In some embodiments, after a multicast frame, the MU ACK frame (ormultiplexed ACK frames or multiplex BA frames) follow after an IFSinterval. In such embodiments, the multicast group that has beenannounced by the AP has an inherent order of the STAs. Such inherentorder is used to assign the sub-bands to individual STAs formultiplexing their ACK/BA response (in a similar manner as explainedabove). However, the AP identifies the bandwidth that can be used formultiplexing the ACK or BA response (denote this parameter byMulticastACKBW), where the value of MulticastACKBW may be a priori knownto the STAs that belong to a multicast group, e.g., during theannouncement of the multicast group. Alternatively, the AP may announcea fixed MulticastACKBW value for all multicast groups (either within theBeacon frame or during association).

In some of the above embodiments, after a multicast frame that has asingle MPDU (whether a MU BAR frame is present or not), a MU ACK framemay follow that is multiplexed with several ACK frames. Note that theSTAs that have not decoded the multicast payload correctly may not sendan ACK frame. The AP (the sender of the multicast payload) can concludefrom the presence of an ACK frame in a given sub-band whether a STA hassent the ACK frame. In some of the above embodiments, after a multicastframe that has multiple MPDUs (whether a MU BAR frame is present ornot), a MU ACK frame may follow that is multiplexed with several BAframes.

In some embodiments, the MU BAR frame has the same structure as an802.11-based BlockAckReq frame or Multi-TID BlockAck frame but with thefollowing differences: (a) If Multi-TID BlockAck frame is used, the“Per-TID info” has the identification of each STA (AID or PAID) that isexpected to respond. In some embodiments, this field is the only fieldpresent in each “BAR Information field.” In some of the aboveembodiments where the identification of STAs is not included in a MU BARframe, the 802.11-based BlockAckReq frame is used, (b) The “BAR Control”field includes AcknowledgmentBW, (c) The “BAR Control” field may includean identification of the multicast group, denoted by MulticastID, (d)The “BAR Control” field includes “Block ACK starting sequence control.”Note that “Block ACK starting sequence control” applies to all the STAsthat are expected to respond with a BA frame hence it is present in “BARControl” instead of each “BA Information field”). Not that in the aboveembodiments, the “BAR Control” field may have 2-4 octets length in orderto accommodate AcknowledgmentBW, MulticastID, and “Block ACK startingsequence control” fields. A frame with the above fields may be denotedas Multicast BAR and may be assigned a new frame sub-type in the MACheader. The RA address of such frame is set to Broadcast address. In theabove embodiments, the “BAR ACK Policy” in the “BAR Control” field isset to a FALSE value, which means that the STAs do not set anacknowledgment to the BAR frame. In the above embodiments, the“Multi-TID” bit in the “BAR Control” field may be a reserved field. Insome embodiments where the same BAR frame with the same sub-type isused, the Multi-TID bit may be set to a TRUE value to indicate that theBAR frame is a MulticastBAR frame.

FIG. 14 illustrates a schematic diagram of an example of a downlinkOFDMA frame 1400 and an uplink MU frame 1420 (or MU ACK frame) from aset of STAs. A similar exchange as in FIG. 7 is illustrated in FIG. 14except that the STAs that receive payloads in the DL OFDMA PPDU 1400send an UL MU PPDU. FIG. 7 shows that the MU ACK frame is sent in ULOFDMA format where FIG. 14 shows that the ACK frames are sent in UL MUMIMO format where there are restrictions on the number of spatialstreams that each STA uses in the MU ACK frame (more details explainedbelow). Note that in the HE SIG A or HE SIG-B part of the DL OFDMA frame1400, the AP indicates whether the ACK/BA frames can be multiplexed withUL OFDMA format or UL MU format.

In FIG. 14, a DL OFDMA transmission is followed by a PPDU that includesACKs and/or BAs in the UL MU MIMO format from the STAs that have apayload in the DL OFDMA frame 1400, where their ACK policy field in theQoS control field is set to 00 or “Normal Ack or Implicit Block AckRequest.” First, an AP transmits a DL OFDMA PPDU (e.g., 1400) in a HEPPDU format. The HE PPDU format is composed of a header 1401 having theLegacy PLCP, the HE PLCP (e.g., HE SIG-A, HE SIG-B) and the PSDU (e.g.,1401). The AP transmits the payloads through sub-bands of possiblyvarying bandwidth, and possibly non-contiguous hands for a given STA.After the SIFS from receiving the DL OFDMA PPDU, all the STAs that havetheir ACK Policy field in the QoS control field is set to 00 or “NormalAck or Implicit Block Ack Request,” transmit their ACK or BA framessimultaneously in UL MU MIMO format, which collectively is called MUACK. The MU ACK frame (e.g., 1420) is composed of the Legacy PLCP (e.g.,1421) including the HE SIG-A symbol, which is transmitted by all theSTAs that participate in forming the MU ACK, and the PSDU (e.g., 1424).Since the ACK/BA frames are sent in the UL MU MIMO format, there aresome restrictions on the number of spatial streams (SS) that each STAcan use, which are explained below. Note that in the HE SIG A or HESIG-B part (e.g., 1401) of the DL OFDMA frame 1400, the AP indicateswhether the ACK/BA frames can be multiplexed with a UL OFDMA format or aUL MU format.

FIG. 15 illustrates a schematic diagram of an example of a downlinkframe 1500 and an uplink frame 1420 for a multiuser exchange among WLANdevices. A similar exchange as in FIG. 14 is illustrated in FIG. 15except that the downlink transmission has a DL MU MIMO format.

FIG. 15 illustrates a DL, MU MIMO transmission which is followed by aPPDU that includes ACKs and/or BAs in the UL MU MIMO format from theSTAs that have a payload in the DL MU MIMO frame 1500, where their ACKPolicy field in the QoS control field is set to 00 or “Normal Ack orimplicit Block Ack Request,” First, an AP transmits a DL MU MIMO frame(e.g., 1500) in a HE PPDU format. The HE PPDU format is composed of aheader 1401 having the Legacy PLCP, the HE PLCP (e.g., HE SIG-A, HESIG-B) and the PSDU (e.g., 1501). After the SIFS from receiving the DLMU MIMO PPDU 1500), all the STAs that have their ACK policy field in theQoS control field set to 00 or “Normal Ack or Implicit Block AckRequest,” transmit their ACK or BA frames simultaneously in the UL MUMIMO format, which collectively is called a MU ACK. The MU ACK frame(e.g., 1420) is composed of the Legacy PLCP (e.g., 1421) including theHE SIG-A symbol, which is transmitted by all the STAs that participatein forming the MU ACK, and the PSDU (e.g., 1424). Particularly, the MUACK frame in the UL MU MIMO format has several HE LTF symbols that aredenoted as “Set of LTFs” and are explained below. Since the ACK/BAframes are sent in the UL MU MIMO format, there are some restrictions onthe number of spatial streams (SS) that each STA can use, which areexplained below. Note that in the HE SIG A or HE SIG-B part (e.g., 1401)of the DL MU MIMO frame 1500, the AP indicates whether the ACK/BA framescan be multiplexed with the UL OFDMA format or the UL MU format.

In forming the MU ACK frame (e.g., 1420), the partial HE PLCP part ofthe frame which consists of HE SIG-A, if present, is formed as with FFTsize 64 for the bandwidth of 20 MHz. If the immediately preceding DLOFDMA PPDU (e.g., 1500) has 40 MHz, then the partial HE PLCP part canhave two identical parts with total bandwidth of 40 MHz. If theimmediately preceding DL OFDMA PPDU has 80 MHz, then the partial HE PLCPpart can have four identical parts with total bandwidth of 40 MHz. Ifthe immediately preceding DL OFDMA PPDU has 160 MHz or 80+80 MHz, thenthe partial HE PLCP part can have eight identical parts with totalbandwidth of 160 MHz. The encoding of different fields of the SIG-A partcan be with the same values that has been indicated in the immediatelypreceding DL OFDMA frame Particularly, all the parameters in theTXVECTOR that relate to the HE SIG-A are set to values that are a prioriknown but the parameter CH_BANDWIDTH in the TXVECTOR is set to the samevalue as in CH_BANDWIDTH in the RXVECTOR of the immediately preceding DLOFDMA PPDU. In other embodiments, the fields in HE SIG-A are encodedwith a fixed value that the AP announces, or fixed values such that allthe STAs that participate in forming the MU ACK frame can use identicalvalues for all of the fields in the HE SIG-A symbols. In some otherembodiments, only the first symbol of the HE SIG-A symbols, sometimesknown as HE SIG-A1, is only present in the partial HE PLCP in the MU ACKframe.

In forming the PSDU part of an MU ACK frame, a STA can set the TXVECTORparameter GI_TYPE of a MU ACK frame carried in the HE PPDU format (withpartial PLCP or preamble header as described above) to the RXVECTORparameter GI_TYPE of a frame eliciting the response. In otherembodiments, a STA can set the TXVECTOR parameter GI_TYPE of a MU ACKframe carried in the HE PPDU format (with partial PLCP or preambleheader as described above) to the LONG_GI (for the FFT size of 256, theLONG_GI may have values such as 1.6 μs or 3.2 μs).

In forming the PSDU part of an MU ACK frame, a STA may set the TXVECTORparameter FORMAT to HE, set the TXVECTOR parameter N_TX to one, and setthe TXVECTOR parameter FCC_CODING to BCC_CODING. The STA also may setthe TXVECTOR parameter MCS to value 0 (or MCS0). In other embodiments, aSTA may set the TXVECTOR parameter MCS to the value of a MUACK-MCSparameter that has been indicated by the AP in the immediately precedingDL OFDMA frame (e.g., 1400). The MUACK-MCS parameter is indicated in theMUACK-MCS field of the HE control field of the immediately preceding DLOFDMA frame (e.g., 1400). In other embodiments, the MCS parameter in theTXVECTOR of the MU ACK frame can be set to the parameter MUACKMCS. TheAP announces the parameter MUACKMCS during association, or in Beaconframes. In other embodiments, the parameter MUACKMCS is set to a fixedvalue a priori, such that all the STAs that participate in forming theMU ACK frame can use identical values for this parameter.

In the embodiments, such as the examples shown in FIG. 14 and FIG. 15,instead of SUBCARRIERS_LIST, there is a need to indicate what set ofLTFs each STA can use to send its ACK/BA frame in the UL MU MIMO format.Each STA that has a payload in the DL MU MIMO frame (e.g., 1500) andintends to place its ACK/BA frame in the MU ACK/BA after the DL MU MIMOframe, can select a unique index denoted by LTF_index (which is notshared by other STAs in the same DL MU frame) and intends to use thisindex to define the set of HE LTF symbols (e.g., 1422) that the STA canplace at the beginning of its MU ACK/BA frame as shown in FIG. 14 andFIG. 15.

In the case of FIG. 15 where the DL MU frame is a DL MU MIMO frame(e.g., 1500), there is a GID indication in HE SIG-A or HE SIG-B (e.g.,1401) where it indicates all the STAs that are part of the GID and mayhave a payload in the DL PPDU. Additionally, there is an orderassociated per STA in the GID, and if the NSS associated with this orderis non-zero, the GID indicates that the STA has a payload in the DL MUMIMO PPDU. Given the GID, the order of each STA in the GID, and whetherthe associated NSS in the GID is zero or non-zero, each STA that has apayload in the DL MU MIMO frame can select an index, LTF_index, which isused to define the set of HE LTF symbols (e.g., 1422) that they use.

In some aspects, a HE STA receives a HE DL MU MIMO PPDU (e.g., 1500)that includes a GID associated with the HE STA and a non-zero NSSassociated with the same order as the order of the HE STA in the GID. Ifthe transmitter of the HE DL MU MIMO PPDU has indicated in the HE SIG(e.g., 1401) that the MU ACK frame can be in the UL MU MIMO format, thenthe HE STA creates the set of HE LTF symbols (e.g., 1422) for the MU ACKbased on a row index of a P matrix for the LTF symbols where the rowindex is the same order as the order of the HE STA in the GID of the HEDL MU MIMO PPDU. The row index is the LTF_index and is used to preparethe set of HE LTF symbols that they use.

In the case of FIG. 15 where the DL MU PPDU is a DL OFDMA PPDU (e.g.,1500), each STA that has a payload in the DL MU MIMO frame and intendsto place its ACK/BA frame in the MU ACK/BA after the DL MU frame,selects a unique index (which is not shared by other STAs in the same DLMU frame) and uses the selected index to define the set of HE LTFsymbols that the STA can place at the beginning of its MU ACK/BA frameas shown in FIG. 15. However, unlike FIG. 14, where there is an explicitindex associated with each STA in the GID, there is no such indexingsimilarly defined in FIG. 15. In some embodiments, an implicitindication may be used to inform each STA of their LTF_index to be usedfor a MU ACK/BA frame. Such implicit indication works as follows.

In some aspects, a HE STA that receives a HE DL OFDMA PPDU (e.g., 1400),where the AID/PAID or any related ID of the HE STA is indicated in theHE SIG-B field (e.g., 1401) of the HE OFDMA PPDU. If the transmitter ofthe HE DL OFDMA PPDU has indicated in the HE SIG (e.g., 1401) that theMU ACK frame 1420) can be in the UL MU MIMO format, then the HE STAcreates the set of HE LTF symbols for the MU ACK based on a row index ofthe P matrix for the LTF symbols, where the row index is the order wherethe sub-band assignment of the HE STA appears in the DL OFDMA PPDU.

In other aspects, a HE STA that receives a HE DL OFDMA PPDU 1400), wherethe AID/PAID or any related ID of the HE STA is indicated in the HESIG-B field (e.g., 1401) of the HE OFDMA PPDU. If the transmitter of theHE DL OFDMA PPDU has indicated in the HE SIG (e.g., 1401) that the MUACK frame (e.g., 1420) can be in the UL MU MIMO format, the HE SIGsymbol of the DL OFDMA PPDU may carry a value called LTF row (with sizeof 3 or 4 bits) for each STA whose sub-band assignment appears in the HESIG-B. Note that if LTF row is set to a reserved value, then the LTF rowreflects that the HE STA may not send an MU ACK/BA frame. In turn, theHE STA creates the set of HE LTF symbols for the MU ACK based on a rowindex of the P matrix for the LTF symbols where the row index is thesame value as the associated LTF row for the HE STA (that appears in theHE SIG symbol of the HE DL OFDMA PPDU).

Once the LTF_index is obtained by a HE STA that intends to participatein forming an MU ACK frame, the HE STA prepares the set of LTF symbols(e.g., 1422) to be used as in FIG. 14 and FIG. 15 as follows. The STAcreates a set of HE LTF symbols with possibly 4 μs symbol length (pereach LTF symbol) or possibly with 8 μs or 12 μs length depending onimplementation. The set of HE LTF symbols are going to be N_LTF symbols,where N_LTF is either the same number as the number of LTF symbols inthe previous DL MU MI MO frame, or it is explicitly indicated in the HESIG symbol of the previous DL MU MIMO frame. In turn, the STA selectsthe set of LTF symbols from the LTF_index row that are created based onan orthogonal matrix that is denoted by P (Orthogonal P matrix). TheOrthogonal P matrix may have many forms. In one embodiment, the P matrixwith size four has the following rows: First row of the P matrix is: 1,−1, 1, 1; second row of the P matrix is: 1, 1, −1, 1; third row of the Pmatrix is: 1, 1, 1, −1; and fourth row of the P matrix is: −1, 1, 1, 1.In another embodiment, the P matrix with size eight has the followingrows: First row of the P matrix is: 1, −1, 1, 1, 1, −1, 1, 1; second rowof the P matrix is: 1, 1, −1, 1, 1, 1, −1, 1; third row of the P matrixis: 1, 1, 1, −1, 1, 1, 1, −1; fourth row of the P matrix is: −1, 1, 1,1, −1, 1, 1, 1; fifth row of the P matrix is: 1, −1, 1, 1, −1, 1, −1,−1; sixth row of the P matrix is: 1, 1, −1, 1, −1, −1, 1, −1; seventhrow of the P matrix is: 1, 1, 1, −1, −1, −1, −1, 1; and eighth row ofthe P matrix is: −1, 1, 1, 1, 1, −1, −1, −1. Once a row of theorthogonal P matrix is selected, a HE STA arranges several HE LTFsymbols sequentially but the set of LTF symbols get multiplied by therow of the orthogonal P matrix. This set of LTF symbols appear as “Setof HE LTFs” (e.g., 1422) as in FIG. 14 and FIG. 15. This operationcauses that the set of HE LTF symbols created using two different rowsof an orthogonal matrix can be orthogonal.

Note that while in FIGS. 7, 14 and 15, the bandwidth of the MU ACK frameis the same as the DL OFDMA frame, in general it is possible that thebandwidth of the MU ACK is narrower than the BW of the DL OFDMA frame.However, it is expected that the AP establishes the understanding of thebandwidth of the MU ACK ahead of time so that all of the STAs know thebandwidth of the MU ACK that they are going to participate in forming.In one instance, the bandwidth of the MU ACK may be fixed to 20 MHzregardless of the bandwidth of the DL OFDMA frame, or the bandwidth ofthe MU ACK may be fixed to 40 MHz when DL OFDMA PPDUs has a bandwidth of40 MHz or more. The indication of the bandwidth of the MU ACK frame canbe performed in multiple ways: (a) it may be identified as an indicationto all STAs either in Beacon frames or during association time, (b) orit may be identified in each DL OFDMA frame within the HE SIG-A or HESIG-B, the AP notifies the STAs (that are expecting a DL payload fromthe AP) of the bandwidth for the expected MU ACK frame. Given thebandwidth of the MU ACK frame, the bandwidth of all the sub-bandsassigned to an ACK or a BA frame are the same, and the total number ofsub-bands for ACK/BA multiplexing is given in some embodiments.

In forming the partial HE PLCP and/or PSDU part of an MU ACK frame, aSTA can set the TXVECTOR parameter GI_TYPE of a MU ACK frame carried inthe HE PPDU format (with partial PLCP or preamble header as describedabove) to the RXVECTOR parameter GI_TYPE of a frame eliciting theresponse. In other embodiments, a STA can set the TXVECTOR parameterGI_TYPE of a MU ACK frame carried in the HE PPM format (with partialPLCP or preamble header as described above) to the LONG_GI (for the FFTsize of 256, LONG_GI may have values such as 1.6 μs or 3.2 μs). If a BAframe is sent as an immediate response to either an implicit BA requestcarried in an HE MU PPDU, the MU ACK frame (that contains the BA frame)can be carried in HE PPDU with the setting as described above. The rateand bandwidth of the BA is selected as described above using CODING,MCS, GI parameters of the RXVECTOR parameters of the HE DL OFDMA PPDU inorder to set CODING, MCS, GI parameters of the TXVECTOR parameters ofthe MU ACK frame. If an ACK frame is sent as an immediate response toeither an implicit BA request carried in an HE OFDMA PPDU, the MU ACKframe (that contains the BA frame) can be carried in HE PPDU with thesetting as described above. The rate and bandwidth of the BA is selectedas described above using CODING, MCS, GI parameters of the RXVECTORparameters of the HE DL OFDMA PPDU in order to set CODING, MCS, GIparameters of the TXVECTOR parameters of the MU ACK frame.

While receiving an MU ACK frame transmitted in the HE PPDU format withdetails described above, the AP uses the RXVECTOR parameterLTF_Set_Index to identify which STA has responded with ACK and BAframes. The MAC entity compares the RXVECTOR parameter LTF_Set_Indexwith the order of the TXVECTOR parameter SUBCARRIERS_LIST of thepreceding HE OFDMA PPDU sent, and identifies which of the STAs hasparticipated in forming the MU ACK. Specially for ACK frames, the APdoes not know which STA has sent the ACK frame since there is no TAfield in the received ACK frame (ACK frame only has RA address).However, in some embodiments where the LTF_Set_Index of the TX VECTOR ofa HE OFDMA PPDU and the order of SUBCARRIERS_LIST of the TXVECTOR of theimmediately following MU ACK are the same for each STA that receives apayload in the HE OFDMA PPDU and that participates in forming the MU ACKframe, the AP can verify the presence of LTF_Set_Index in the RX VECTORof the received MU ACK frame. If the ACK or BA frame is not present inthe given SUBCARRIERS_LIST of the received MU ACK frame, the AP infersthe STA that has not sent an ACK or BA frame using the given order ofthe SUBCARRIERS_LIST (in the DL OFDMA and MU ACK exchange). If a BA orACK frame is present in the given SUBCARRIERS_LIST of the received MUACK frame and if the frame is an ACK frame, then the AP can furtherinfer which STA has sent the ACK frame (see FIG. 15).

Referring back to FIG. 13, an AP may use both the QoS control field andthe HECE sub-field 1320 in a DL payload to inform the STA, that has apayload in the DL MU frame, on where to locate the sub-band that the STAintends to use to place its ACK or BA frame in the immediatelymultiplexed-ACK/BA frame. To do so, for each payload in a DL MU frame,an AP uses the HECE sub-field 1320 in the MAC header and fills thedesignated “LTF Set Index” field. Note that the LTF Set Index field mayhave additional sub-fields such as “Size of LTF Set,” where collectivelythese sub-fields explicitly identify all the right set of LTF symbolsthat the STA intends to use to place its ACK/BA frame in the ULmultiplexed ACK/BA frame. Yet in other embodiments, the AP may add anAction Management frame to the DL data payload (hence forming an AMPDU)where the management frame identifies the sub-bands that the STA intendsto use to place its ACK/BA frame in the UL multiplexed ACK/BA frame. Thestructure of the HT Control (HTC) field and its possible extension isshown in FIG. 13. When the HECEI field 1311 in the HT Control Middle1310 is set to 1, then the HECE sub-field exists, otherwise the HECEsub-field does not exist. The HECE sub-field 1320 carries the followinginformation: ACK/BA Sub-bands, LTF Set Index, ULDL, Bandwidth, sub-bandresolution, MCS and NSS per all the sub-bands with the mentionedsub-band resolution, queue size per TID, or alternatively queue size perAC. Note that some of above sub-fields are optional or may be skippedsince it is also reported in HTC or QoS fields. For instance, in oneembodiment, the queue size may only be reported (per an AC or all ACs)in the QoS control field and no indication of queue size is reported inHECE sub-field 1320. However, in another embodiment, it may bebeneficial to have the queue size per AC or per TID, hence these valuesare reported in the HECE sub-field 1320.

FIGS. 16A-16C illustrate flow charts of examples of multi-useraggregation methods for data and control frames. For explanatory andillustration purposes, the example processes 1610, 1620 and 1630 may beperformed by the wireless communication devices 111-115 of FIG. 1 andtheir components such as a baseband processor 210, a MAC processor 211,a MAC software processing unit 212, a MAC hardware processing unit 213,a PHY processor 215, a transmitting signal processing unit 280 and/or areceiving signal processing unit 290; however, the example processes1610, 1620 and 1630 are not limited to the wireless communicationdevices 111-115 of FIG. 1 or their components, and the example processes1610, 1620 and 1630 may be performed by some of the devices shown inFIG. 1, or other devices or components. Further for explanatory andillustration purposes, the blocks of the example processes 1610, 1620and 1630 are described herein as occurring in serial or linearly.However, multiple blocks of the example processes 1610, 1620 and 1630may occur in parallel. In addition, the blocks of the example processes1610, 1620 and 1630 need not be performed in the order shown and/or oneor more of the blocks/actions of the example processes 1610, 1620 and1630 need not be performed. Various examples of aspects of thedisclosure are described below as clauses for convenience. These areprovided as examples, and do not limit the subject technology. As anexample, some of the clauses described below are illustrated in FIGS.16A through 16C.

Clause A. A station for facilitating multi-user communication in awireless network, the station comprising: one or more memories; and oneor more processors coupled to the one or more memories, the one or moreprocessors configured to cause: determining a control field within afirst frame of a downlink transmission for a plurality of stations,wherein the control field is located in a payload section of the firstframe, wherein the control field indicates scheduling information fortransmitting a second frame; generating the second frame, for amulti-user uplink transmission with the plurality of stations, based onthe scheduling information; and providing for transmission of the secondframe based on the control field of the first frame as part of themulti-user uplink transmission with the plurality of stations.

Clause B. A non-transitory computer-readable storage medium storingcomputer-executable instructions that, when executed by one or moreprocessors, cause one or more processors to perform operations, theoperations comprising: identifying scheduling information for aplurality of stations to transmit an uplink frame as part of amulti-user uplink transmission with the plurality of stations;generating a downlink frame of a downlink transmission for the pluralityof stations, wherein the downlink frame includes a control field locatedin a payload section of the downlink frame, wherein the control fieldindicates the scheduling information; and providing for transmission ofthe downlink frame.

Clause C. A computer-implemented method of facilitating multi-usercommunication in a wireless network, the method comprising: generating amulti-user frame for downlink transmission directed to a plurality ofstations, wherein the multi-user frame includes a control field locatedin a payload section of the multi-user frame, wherein the control fieldindicates scheduling information for each of the plurality of stationsto transmit an uplink frame as part of a multi-user uplink transmissionwith the plurality of stations; and providing for transmission themulti-user frame.

In one or more aspects, additional clauses are described below.

A method comprising one or more methods or operations described herein.

An apparatus comprising one or more memories (e.g., 240, one or moreinternal, external or remote memories, or one or more registers) and oneor more processors (e.g., 210) coupled to the one or more memories, theone or more processors configured to cause the apparatus to perform oneor more methods or operations described herein.

An apparatus comprising means e.g., 210) adapted for performing one ormore methods or operations described herein.

A computer-readable storage medium (e.g., 240, one or more internal,external or remote memories, or one or more registers) comprisinginstructions stored therein, the instructions comprising code forperforming one or more methods or operations described herein.

The embodiments provided herein have been described with reference to awireless LAN system; however, it can be understood that these solutionsare also applicable to other network environments, such as cellulartelecommunication networks, wired networks, etc.

An embodiment of the present disclosure may be an article of manufacturein which a non-transitory machine-readable medium (such asmicroelectronic memory) has stored thereon instructions which programone or more data processing components (generically referred to here asa “processor” or “processing unit”) to perform the operations describedherein. In other embodiments, some of these operations may be performedby specific hardware components that contain hardwired logic (e.g.,dedicated digital filter blocks and state machines). Those operationsmay alternatively be performed by any combination of programmed dataprocessing components and fixed hardwired circuit components.

In some cases, an embodiment of the present disclosure may be anapparatus (e.g., an AP STA, anon-AP STA, or another network or computingdevice) that includes one or more hardware and software logic structurefor performing one or more of the operations described herein. Forexample, as described above, the apparatus may include a memory unit,which stores instructions that may be executed by a hardware processorinstalled in the apparatus. The apparatus may also include one or moreother hardware or software elements, including a network interface, adisplay device, etc.

In one aspect, a method may be an operation, an instruction, or afunction and vice versa. In one aspect, a clause may be amended toinclude some or all of the words (e.g., instructions, operations,functions, or components) recited in other one or more clauses, one ormore sentences, one or more phrases, one or more paragraphs, and/or oneor more claims.

To illustrate the interchangeability of hardware and software, itemssuch as the various illustrative blocks, modules, components, methods,operations, instructions, and algorithms have been described generallyin terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application.

A reference to an element in the singular is not intended to mean oneand only one unless specifically so stated, but rather one or more. Forexample, “a” module may refer to one or more modules. An elementproceeded by “a,” “an,” “the,” or “said” does not, without furtherconstraints, preclude the existence of additional same elements.

Headings and subheadings, if any, are used for convenience only and donot limit the invention. The word exemplary is used to mean serving asan example or illustration. To the extent that the term include, have,or the like is used, such term is intended to be inclusive in a mannersimilar to the term comprise as comprise is interpreted when employed asa transitional word in a claim. Relational terms such as first andsecond and the like may be used to distinguish one entity or action fromanother without necessarily requiring or implying any actual suchrelationship or order between such entities or actions.

Phrases such as an aspect, the aspect, another aspect, some aspects, oneor more aspects, an implementation, the implementation, anotherimplementation, some implementations, one or more implementations, anembodiment, the embodiment, another embodiment, some embodiments, one ormore embodiments, a configuration, the configuration, anotherconfiguration, some configurations, one or more configurations, thesubject technology, the disclosure, the present disclosure, othervariations thereof and alike are for convenience and do not imply that adisclosure relating to such phrase(s) is essential to the subjecttechnology or that such disclosure applies to all configurations of thesubject technology. A disclosure relating to such phrase(s) may apply toall configurations, or one or more configurations. A disclosure relatingto such phrase(s) may provide one or more examples. A phrase such as anaspect or some aspects may refer to one or more aspects and vice versa,and this applies similarly to other foregoing phrases.

A phrase “at least one of” preceding a series of items, with the terms“and” or “or” to separate any of the items, modifies the list as awhole, rather than each member of the list. The phrase “at least one of”does not require selection of at least one item; rather, the phraseallows a meaning that includes at least one of any one of the items,and/or at least one of any combination of the items, and/or at least oneof each of the items. By way of example, each of the phrases “at leastone of A, B, and C” or “at least one of A, B, or C” refers to only A,only B, or only C; any combination of A, B, and C; and/or at least oneof each of A. B, and C.

It is understood that the specific order or hierarchy of steps,operations, or processes disclosed is an illustration of exemplaryapproaches. Unless explicitly stated otherwise, it is understood thatthe specific order or hierarchy of steps, operations, or processes maybe performed in different order. Some of the steps, operations, orprocesses may be performed simultaneously. The accompanying methodclaims, if any, present elements of the various steps, operations orprocesses in a sample order, and are not meant to be limited to thespecific order or hierarchy presented. These may be performed in serial,linearly, in parallel or in different order. It can be understood thatthe described instructions, operations, and systems can generally beintegrated together in a single software/hardware product or packagedinto multiple software/hardware products.

The disclosure is provided to enable any person skilled in the art topractice the various aspects described herein. In some instances,well-known structures and components are shown in block diagram form inorder to avoid obscuring the concepts of the subject technology. Thedisclosure provides various examples of the subject technology, and thesubject technology is not limited to these examples. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the principles described herein may be applied to otheraspects.

All structural and functional equivalents to the elements of the variousaspects described throughout the disclosure that are known or later cometo be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. § 112, sixth paragraph, unless theelement is expressly recited using a phrase means for or, in the case ofa method claim, the element is recited using the phrase step for.

The title, background, brief description of the drawings, abstract, anddrawings are hereby incorporated into the disclosure and are provided asillustrative examples of the disclosure, not as restrictivedescriptions. It is submitted with the understanding that they will notbe used to limit the scope or meaning of the claims. In addition, in thedetailed description, it can be seen that the description providesillustrative examples and the various features are grouped together invarious implementations for the purpose of streamlining the disclosure.The method of disclosure is not to be interpreted as reflecting anintention that the claimed subject matter requires more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed configuration or operation. The following claims arehereby incorporated into the detailed description, with each claimstanding on its own as a separately claimed subject matter.

The claims are not intended to be limited to the aspects describedherein, but are to be accorded the full scope consistent with thelanguage claims and to encompass all legal equivalents. Notwithstanding,none of the claims are intended to embrace subject matter that fails tosatisfy the requirements of the applicable patent law, nor can they beinterpreted in such a way.

What is claimed is:
 1. A station for facilitating multi-usercommunication in a wireless network, the station comprising: one or morememories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: determining acontrol field within a first frame of a downlink transmission for aplurality of stations, wherein the control field is located in a mediaaccess control (MAC) header of a trigger MAC PDU (MPDU) within a payloadsection of the first frame; determining whether an extension indicationfield in the control field indicates that the control field includes anextended control field, the extended control field indicating one ormore sub-bands assigned to the station, wherein the control fieldindicates scheduling information for transmitting a second frame whenthe extension indication field indicates that the control field includesthe extended control field; generating the second frame, for amulti-user uplink transmission with the plurality of stations, based onthe scheduling information; and providing for transmission of the secondframe using the one or more sub-bands based on the control field of thefirst frame as part of the multi-user uplink transmission with theplurality of stations.
 2. The station of claim 1, wherein the schedulinginformation includes an assignment of one or more resource units to thestation, wherein the station utilizes the one or more assigned resourceunits for the multi-user uplink transmission with the plurality ofstations.
 3. The station of claim 2, wherein the second frame includesan acknowledgment (ACK) frame or a block acknowledgment (BA) frameutilizing the one or more assigned resource units.
 4. The station ofclaim 3, wherein the first frame includes a multicast media accesscontrol (MAC) protocol data unit (MPDU), addressed to a set of stations,and the scheduling information requests an ACK or BA frame from one ormore of the stations in the set of stations addressed by the multicastMPDU.
 5. The station of claim 2, wherein the one or more resource unitsidentify one or more sub-bandwidths of a channel bandwidth of thedownlink transmission.
 6. The station of claim 1, wherein the secondframe is a trigger-based physical layer convergence procedure (PLCP)protocol data unit (PPDU) that carries an immediate acknowledgment tothe first frame.
 7. The station of claim 6, wherein the schedulinginformation includes a length of the trigger-based PPDU.
 8. The stationof claim 1, wherein the control field is a High Efficiency Control fieldwithin the MAC header of the trigger MPDU.
 9. The station of claim 1,wherein the control field is located in a trigger MAC PDU (MPDU) and thetrigger MPDU is a first MPDU in an aggregated-MPDU (A-MPDU) within thepayload section of the first frame.
 10. The station of claim 9, whereinthe trigger MPDU is a control frame that carries the control field in apayload of the trigger MPDU.
 11. The station of claim 1, wherein each ofthe downlink transmission and the multi-user uplink transmission are oneor more of an orthogonal frequency-division multiple access (OFDMA)transmission or a multi-user multi-input multi-output (MU MIMO)transmission.
 12. A non-transitory computer-readable storage mediumstoring computer-executable instructions that, when executed by one ormore processors, cause one or more processors to perform operations, theoperations comprising: identifying scheduling information for aplurality of stations to transmit an uplink frame as part of amulti-user uplink transmission with the plurality of stations;generating a downlink frame of a downlink transmission for the pluralityof stations, wherein the downlink frame includes a control field locatedin a media access control (MAC) header of a trigger MAC PDU (MPDU)within a payload section of the downlink frame, wherein the controlfield includes an extension indication field that indicates whether thecontrol field includes an extended control field, the extended controlfield indicating one or more sub-bands assigned to the station, whereinthe control field indicates the scheduling information when theextension indication field indicates that the control field includes theextended control field; and providing for transmission the downlinkframe.
 13. The non-transitory computer-readable storage medium of claim12, wherein the downlink frame includes a multicast MAC protocol dataunit (MPDU), addressed to a set of stations, and the schedulinginformation requests an acknowledgment (ACK) or block ACK (BA) framefrom one or more of the stations in the set of stations addressed by themulticast MPDU.
 14. The non-transitory computer-readable storage mediumof claim 12, wherein the control field is a High Efficiency controlfield within the MAC header of the trigger MPDU.
 15. The non-transitorycomputer-readable storage medium of claim 12, wherein the control fieldis located in a trigger MAC protocol data unit (MPDU) and the triggerMPDU is a first MPDU in an aggregated-MPDU (A-MPDU) within the payloadsection of the downlink frame.
 16. The non-transitory computer-readablestorage medium of claim 15, wherein the trigger MPDU is a control framethat carries the control field in a payload of the trigger MPDU.
 17. Thenon-transitory computer-readable storage medium of claim 12, wherein theuplink frame is a trigger-based physical layer convergence procedure(PLCP) protocol data unit (PPDU) that carries an immediateacknowledgment to the downlink frame.
 18. A computer-implemented methodof facilitating multi-user communication in a wireless network, themethod comprising: generating a multi-user frame for downlinktransmission directed to a plurality of stations, wherein the multi-userframe includes a control field located in a media access control (MAC)header of a trigger MAC PDU (MPDU) within a payload section of themulti-user frame, wherein the control field includes an extensionindication field that indicates whether the control field includes anextended control field, the extended control field indicating one ormore sub-bands assigned to the station, wherein the control fieldindicates scheduling information for each of the plurality of stationsto transmit an uplink frame as part of a multi-user uplink transmissionwith the plurality of stations when the extension indication fieldindicates that the control field includes the extended control field;and providing for transmission the multi-user frame.